Method and apparatus for performing initial access (IA) in a wireless communication system

Abstract

The present disclosure relates to a 5G communication system or a 6G communication system for supporting higher data rates beyond a 4G communication system such as long term evolution (LTE). The present invention generally relates to wireless communications and, more particularly, to methods for performing an initial access (IA) procedure in a wireless communication system and to respective communication devices as well. According to the present invention, a method for performing IA in a wireless communication system is provided, the method comprising, in a user equipment: based on a demodulation reference signal (DMRS) configuration information for uplink (UL) received from a base station of the wireless communication system, performing selection of a DMRS port; and performing transmission, to the base station, of message Msg3 using the selected DMRS port. The present invention generally provides improvement of the IA procedure for 6G xMIMO systems by using the MU-MIMO technology, and, more particularly, the present invention provides, for the IA procedure, reduction of the likelihood of unsuccessful decoding of Msg3 from physical uplink shared channel (PUSCH) due to a collision between user equipments performing IA, as well as improved accuracy of timing advance (TA) estimation for UL.

Description

METHOD AND APPARATUS FOR PERFORMING INITIAL ACCESS (IA) IN A WIRELESS COMMUNICATION SYSTEM

[0001] The present invention generally relates to wireless communications and, more particularly, to methods of performing an initial access (IA) procedure in a wireless communication system and to respective communication devices as well.

[0002] Considering the development of wireless communication from generation to generation, the technologies have been developed mainly for services targeting humans, such as voice calls, multimedia services, and data services. Following the commercialization of 5G (5th generation) communication systems, it is expected that the number of connected devices will exponentially grow. Increasingly, these will be connected to communication networks. Examples of connected things may include vehicles, robots, drones, home appliances, displays, smart sensors connected to various infrastructures, construction machines, and factory equipment. Mobile devices are expected to evolve in various form-factors, such as augmented reality glasses, virtual reality headsets, and hologram devices. In order to provide various services by connecting hundreds of billions of devices and things in the 6G (6th generation) era, there have been ongoing efforts to develop improved 6G communication systems. For these reasons, 6G communication systems are referred to as beyond-5G systems.

[0003] 6G communication systems, which are expected to be commercialized around 2030, will have a peak data rate of tera (1,000 giga)-level bit per second (bps) and a radio latency less than 100μsec, and thus will be 50 times as fast as 5G communication systems and have the 1 / 10 radio latency thereof.

[0004] In order to accomplish such a high data rate and an ultra-low latency, it has been considered to implement 6G communication systems in a terahertz (THz) band (for example, 95 gigahertz (GHz) to 3THz bands). It is expected that, due to severer path loss and atmospheric absorption in the terahertz bands than those in mmWave bands introduced in 5G, technologies capable of securing the signal transmission distance (that is, coverage) will become more crucial. It is necessary to develop, as major technologies for securing the coverage, Radio Frequency (RF) elements, antennas, novel waveforms having a better coverage than Orthogonal Frequency Division Multiplexing (OFDM), beamforming and massive Multiple-input Multiple-Output (MIMO), Full Dimensional MIMO (FD-MIMO), array antennas, and multiantenna transmission technologies such as large-scale antennas. In addition, there has been ongoing discussion on new technologies for improving the coverage of terahertz-band signals, such as metamaterial-based lenses and antennas, Orbital Angular Momentum (OAM), and Reconfigurable Intelligent Surface (RIS).

[0005] Moreover, in order to improve the spectral efficiency and the overall network performances, the following technologies have been developed for 6G communication systems: a full-duplex technology for enabling an uplink transmission and a downlink transmission to simultaneously use the same frequency resource at the same time; a network technology for utilizing satellites, High-Altitude Platform Stations (HAPS), and the like in an integrated manner; an improved network structure for supporting mobile base stations and the like and enabling network operation optimization and automation and the like; a dynamic spectrum sharing technology via collision avoidance based on a prediction of spectrum usage; an use of Artificial Intelligence (AI) in wireless communication for improvement of overall network operation by utilizing AI from a designing phase for developing 6G and internalizing end-to-end AI support functions; and a next-generation distributed computing technology for overcoming the limit of UE computing ability through reachable super-high-performance communication and computing resources (such as Mobile Edge Computing (MEC), clouds, and the like) over the network. In addition, through designing new protocols to be used in 6G communication systems, developing mechanisms for implementing a hardware-based security environment and safe use of data, and developing technologies for maintaining privacy, attempts to strengthen the connectivity between devices, optimize the network, promote softwarization of network entities, and increase the openness of wireless communications are continuing.

[0006] It is expected that research and development of 6G communication systems in hyper-connectivity, including person to machine (P2M) as well as machine to machine (M2M), will allow the next hyper-connected experience. Particularly, it is expected that services such as truly immersive eXtended Reality (XR), high-fidelity mobile hologram, and digital replica could be provided through 6G communication systems. In addition, services such as remote surgery for security and reliability enhancement, industrial automation, and emergency response will be provided through the 6G communication system such that the technologies could be applied in various fields such as industry, medical care, automobiles, and home appliances.

[0007] The present disclosure relates to method and apparatus for performing an initial access (IA) procedure in a wireless communication system in a wireless communication system.

[0008] According to an aspect of an exemplary embodiment, there is provided a communication method in a wireless communication system.

[0009] Aspects of the present disclosure provide efficient communication methods in a wireless communication system.

[0010] Fig. 1 is an illustration of interaction between a base station and user equipments when the IA procedure according to 5G NR is performed.

[0011] Fig. 2 is a general illustration of the RAR structure according to 5G NR.

[0012] Fig. 3A is an illustration of applying a TA in the user equipment side.

[0013] Fig. 3B is an illustration of the MAC structure of the RAR payload according to 5G NR.

[0014] Fig. 4A is an illustration of 5G NR Type 1 DMRS pattern.

[0015] Fig. 4B is an illustration of 5G NR Type 2 DMRS pattern.

[0016] Fig. 5 is an illustrative diagram of a wireless communication system in which embodiments of the present invention can be implemented.

[0017] Fig. 6 is a flowchart of a method of performing an IA procedure in a wireless communication system according to the present invention.

[0018] Fig. 7 is an illustration of interaction between a base station and user equipments when an IA procedure according to one embodiment of the present invention is performed.

[0019] Fig. 8 is a general illustration of a RAR structure according to one embodiment of the present invention.

[0020] Fig. 9A is an illustration of a DMRS pattern according to one implementation of the present invention.

[0021] Fig. 9B is an illustration of a DMRS pattern according to another implementation of the present invention.

[0022] Fig. 9C is an illustration of a DMRS pattern according to yet another implementation of the present invention.

[0023] Fig. 10 is an illustration of SSB reception by different user equipments in different beams.

[0024] Fig. 11 is an illustration of interaction between a base station and user equipments when an IA procedure according to another embodiment of the present invention is performed.

[0025] FIG. 12 is a block diagram of a terminal or user equipment (UE) according to an embodiment of the disclosure.

[0026] FIG. 13 is a block diagram of a base station (BS) according to an embodiment of the disclosure.

[0027] FIG. 14 is a block diagram of a network entity according to an embodiment of the disclosure.

[0028] The object of the present invention is to improve the IA procedure for 6G xMIMO systems by using the MU-MIMO technology.

[0029] In the context of addressing this technical object, according to the first aspect of the present invention a method of performing initial access (IA) in a wireless communication system is provided. The method provided hereby comprises, in a user equipment: based on a demodulation reference signal (DMRS) configuration information for uplink (UL) received from a base station of the wireless communication system, performing selection of a DMRS port; and performing transmission, to the base station, of message Msg3 using the selected DMRS port.

[0030] In accordance with an embodiment, the transmission of Msg3 is performed in PUSCH, wherein Msg3 includes at least an ID of the user equipment, wherein a DMRS of the selected DMRS port is transmitted within PUSCH. The method further comprises, in the base station, demodulating and decoding Msg3 received from the user equipment, wherein demodulating and decoding Msg3 is performed based on UL channel estimation performed in the base station based on the received DMRS of the selected DMRS port; and transmitting message Msg4 in PDSCH, wherein Msg4 includes, at least, the ID decoded by the base station from Msg3.

[0031] According to an embodiment, the method provided hereby further comprises transmitting, by the base station, the DMRS configuration information, wherein the DMRS configuration information is represented by a bit value. The bit value is accordingly selected in the base station from a predefined set of bit values, wherein each bit value from at least part of the set of bit values indicates at least a number of DMRS ports from which the selection of a DMRS port is to be performed. The set of bit values may be defined in the specification, or preset in the base station and signaled in advance from the base station to the user equipment.

[0032] In accordance with an embodiment, at least one DMRS pattern is preset in the communication system, said DMRS pattern being defined by: two or more CDM groups each defining subcarriers and OFDM symbols in which UL transmission of DMRSs is to be performed; and one or more FD-OCCs. Said DMRS pattern may be based on 5G NR Type 1 DMRS pattern and defined by two CDM groups and two FD-OCCs, or said DMRS pattern may be defined by four CDM groups and one FD-OCC. Each bit value from said at least part of the set of bit values may further indicate a combination of one or more CDM groups and at least one FD-OCC, the combination corresponding to the number of DMRS ports indicated by this bit value. According to an implementation, said at least part of the set of bit values comprises a bit value indicating one DMRS port, which corresponds to the SU-MIMO mode of the PUSCH transmission, and at least one bit value respectively indicating more than one DMRS port, which corresponds to the MU-MIMO mode of the PUSCH transmission. If a bit value indicates more than one DMRS port, said selection of a DMRS port is performed randomly or based on a predefined rule. This predefined rule for selecting a DMRS port may be as follows: (i) based on an index of a SS / PBCH block detected by the user equipment, or (ii) based on the ID of the user equipment included in Msg3, or (iii) based on a combination of (i) and (ii).

[0033] In accordance with an embodiment, the method provided hereby further comprises, in the base station: receiving, from the user equipment, message Msg1 with a random access (RA) preamble transmitted by the user equipment in PRACH, wherein the RA preamble has been randomly selected by the user equipment from a predetermined plurality of RA preambles; and transmitting random access response (RAR) message Msg2 in the PDSCH, wherein Msg2 comprises at least frequency domain and time domain resource allocations for the transmission of Msg3 in PUSCH.

[0034] According to one embodiment, the method further comprises, in base station, further including into Msg2 the bit value representing the DMRS configuration information. In this embodiment, said selection of a DMRS port is performed by the user equipment using the bit value received in Msg2 from the base station. Said receiving Msg1 can further comprise receiving, in PRACH, Msg1 from each of one or more other user equipments performing IA, wherein selection, by the base station, of the bit value representing the DMRS configuration information for inclusion into Msg2 can be based at least partially on RA preambles from the received Msg1s.

[0035] According to another embodiment, the bit value representing the DMRS configuration information is broadcasted by the base station in one of SIBs or in the MIB. In this embodiment, said selection of a DMRS port is performed by the user equipment using the bit value received in the SIB from the base station.

[0036] In accordance with an embodiment, the method provided hereby further comprises, in the base station: based on detecting the RA preamble in Msg1, determining a timing advance (TA) for the transmission of Msg3 in PUSCH, and further including an indication of the TA into Msg2; based on detecting the DMRS in PUSCH, calculating an updated TA, and further including a TA update indication into Msg4. The TA update indication can represent: an indication of a TA adjustment relative to the TA signaled in Msg2, or an indication of the updated TA to replace the TA signaled in Msg2.

[0037] According to the second aspect of the present invention, a method of performing IA in a wireless communication system is provided.

[0038] The method provided hereby comprises, by the base station of the wireless communication system: generating random access response (RAR) message Msg2, wherein DMRS configuration information for UL is included into Msg2; and performing transmission of Msg2. In accordance with an embodiment, the transmission of Msg2 is performed in PDSCH, wherein Msg2 comprises frequency domain and time domain resource allocations for transmission of Msg3.

[0039] Then, the method provided according to the second aspect comprises, in a user equipment: based on the DMRS configuration information from Msg2 received from the base station, performing selection of a DMRS port; and performing transmission, to the base station, of message Msg3 using the selected DMRS port. In accordance with an embodiment, the transmission of Msg3 is performed in PUSCH, wherein Msg3 includes at least an ID of the user equipment, wherein a DMRS of the selected DMRS port is transmitted in PUSCH.

[0040] According to an embodiment, the method further comprises, in the base station, demodulating and decoding Msg3 received from the user equipment, wherein the demodulating and decoding Msg3 is performed based on UL channel estimation performed in the base station based on the received DMRS of the selected DMRS port; and transmitting message Msg4 in PDSCH, wherein Msg4 includes, at least, the ID decoded from the Msg3.

[0041] In accordance with an embodiment, the DMRS configuration information is represented in Msg2 by a bit value, wherein the bit value is accordingly selected in the base station from a predefined set of bit values, wherein each bit value from at least part of the set of bit values indicates at least the number of DMRS ports from which the selection of a DMRS port is to be performed. The set of bit values may be defined in the specification, or may be preset in the base station and signaled in advance from the base station to the user equipment. Accordingly, said including the DMRS configuration information into Msg2 comprises including, by the base station into Msg2, a bit value representing the DMRS configuration information, and said selection of a DMRS port is performed by the user equipment using the bit value received in Msg2.

[0042] According to an embodiment, at least one DMRS pattern is preset in the communication system, said DMRS pattern being defined by two or more CDM groups each defining subcarriers and OFDM symbols in which UL transmission of DMRSs is to be performed, and by one or more FD-OCCs. Said DMRS pattern can be based on 5G NR Type 1 DMRS pattern and defined by two CDM groups and two FD-OCCs, or said DMRS pattern can be defined by four CDM groups and one FD-OCC. Each bit value from said at least part of the set of bit values can further indicate a combination of one or more CDM groups and at least one FD-OCC, the combination corresponding to the number of DMRS ports indicated by said bit value. According to an implementation, said at least part of the set of bit values comprises a bit value indicating one DMRS port, which corresponds to the SU-MIMO mode of the PUSCH transmission, and at least one bit value respectively indicating more than one DMRS port, which corresponds to the MU-MIMO mode of the PUSCH transmission. If a bit value indicates more than one DMRS port, said selection of a DMRS port is performed randomly or based on a predefined rule. This predefined rule for selecting a DMRS port can be as follows: (i) based on an index of a SS / PBCH block detected by the user equipment, or (ii) based on the ID of the user equipment included into Msg3, or (iii) based on a combination of (i) and (ii).

[0043] In accordance with an embodiment, the method provided hereby further comprises, in the base station, receiving, from the user equipment, message Msg1 with a RA preamble transmitted by the user equipment in PRACH, wherein the RA preamble has been randomly selected by the user equipment from a predetermined plurality of RA preambles. Said receiving Msg1 can further comprise receiving, in PRACH, Msg1s from each of one or more other user equipments performing IA, wherein selection, by the base station, of the bit value representing the DMRS configuration information for inclusion into Msg2 can be based at least partially on the RA preambles from the received Msg1s.

[0044] According to an embodiment, the method further comprises, in the base station: based on detecting the RA preamble in Msg1, determining a TA for the transmission of Msg3 in PUSCH and further including an indication of the TA into Msg2; based on detecting the DMRS in PUSCH, calculating an updated TA, and further including a TA update indication into Msg4. The TA update indication can represent: an indication of a TA adjustment relative to the TA signaled in Msg2, or an indication of said updated TA to replace the TA signaled in Msg2.

[0045] In accordance with the third aspect of the present invention, a user equipment in a wireless communication system is provided, the user equipment comprising at least: transceiving units, data processing units, and data storage units. Computer-executable codes are stored in the data storage units, which, when executed by the data processing units, cause the method according to the first aspect to be performed.

[0046] According to the forth aspect of the present invention, a computer-readable storage medium having computer-executable codes stored therein is provided, which, when executed by at least one data processing unit of a user equipment, cause the user equipment to perform the method according to the first aspect.

[0047] In accordance with the fifth aspect of the present invention, a wireless communication system is provided, the system comprising at least a base station, the base station comprising at least: transceiving units, data processing units, and data storage units, wherein the base station is in communication with at least one user equipment comprising at least: transceiving units, data processing units, and data storage units. Computer-executable codes are stored in the data storage units of the base station, and computer-executable codes are stored in the data storage units of the user equipment, wherein the computer-executable codes, when executed by the data processing units of the base station and the user equipment, cause the method according to any embodiment of the first and second aspects to be performed.

[0048] The technical result achievable by the present invention is in providing, for the IA procedure, reduction of the likelihood of unsuccessful decoding of Msg3 from PUSCH due to the collision between user equipments performing IA, as well as in improved accuracy of TA estimation for UL.

[0049] Hereinafter, embodiments of the disclosure will be described in detail with reference to the accompanying drawings.

[0050] In describing the embodiments, while numerous details are set forth for the purpose of illustration, it is understood that some aspects of the disclosure may be practiced with less than all of these details. Numerous variations and alternatives to the details provided herein are possible and are considered within the scope of the disclosure. In some instances, descriptions related to technical contents well-known in the art may be omitted so as to not obscure an understanding of the disclosure, and such omitted descriptions are understood to be within the scope of the disclosure.

[0051] For the same reason, in the accompanying drawings, some elements may be exaggerated, omitted, or schematically illustrated. Further, the size of each element does not completely reflect the actual size. In the drawings, identical or corresponding elements are provided with identical reference numerals or different reference numerals.

[0052] The advantages and features of the disclosure and ways to achieve them will be apparent by making reference to embodiments as described herein in detail in conjunction with the accompanying drawings. However, the disclosure is not limited to the embodiments set forth herein, but may be implemented in various different forms. Other features, aspects, and advantages of the subject matter described herein will become apparent from the disclosure. The following embodiments are merely examples to aid in an understanding of the disclosure and should not be construed to narrow the scope or spirit of the subject matter described herein in any way, but on the contrary, the disclosure covers all modifications, equivalents and alternatives falling within the spirit and scope of the subject matter as defined by the appended claims and equivalents thereof. Throughout the specification, the same or like reference numerals designate the same or like elements. Furthermore, terms which will be described herein are terms defined in consideration of the functions in the disclosure, and may be different according to users, intentions of the operators, or customs. Therefore, the definitions of the terms should be made based on the contents throughout the specification.

[0053] Herein, it will be understood that each block of flowchart illustrations, and combinations of blocks in the flowchart illustrations, may be performed based on computer program instructions. These computer program instructions may be loaded collectively onto at least one processor of a general purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which perform through any one of, or in any combination of, the at least one processor of the computer or other programmable data processing apparatus, create means for performing the functions specified in the flowchart block(s). These computer program instructions may also be stored in a non-transitory computer usable or computer-readable memory that may direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer usable or computer-readable memory produce an article of manufacture including instruction means that perform the function specified in the flowchart block(s). The computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable data processing apparatus to produce a computer executed process such that the instructions that perform on the computer or other programmable data processing apparatus provide steps for executing the functions specified in the flowchart block(s).

[0054] Further, each block may represent a module, segment, or portion of code, which includes one or more executable instructions for executing the specified logical function(s). It should also be noted that in some alternative implementations, the functions noted in the blocks may occur out of the order. For example, two blocks(or functions) shown in succession may in fact be performed substantially concurrently or the blocks may sometimes be performed in the reverse order, depending upon the functionality involved.

[0055] As used in embodiments of the disclosure, a “~unit / module” may refer to a software element or a hardware element, such as a field programmable gate array (FPGA) or an application specific integrated circuit (ASIC), which performs a predetermined function. However, the term including the word “~unit / module” does not always have a meaning limited to software or hardware. The “~unit / module” may be constructed either to be stored in an addressable storage medium or to execute one or more processors. Therefore, the “~unit / module” includes, for example, software elements, object-oriented software elements, components such as class elements and task elements, processes, functions, properties, procedures, sub-routines, segments of a program code, drivers, firmware, micro-codes, circuits, data, database, data structures, tables, arrays, and parameters. The components and functions provided by the “~unit / module” may be either combined into a smaller number of components and a “~unit / module,” or divided into additional components and a “~unit / module.” Moreover, the components and “~units / modules” may be implemented to reproduce one or more central processing units (CPUs) within a device or a security multimedia card. Further, in the embodiments, the “~unit / module” may include one or more processors.

[0056] The entirety of the one or more computer programs may be stored in a single memory device or the one or more computer programs may be divided with different portions stored in different multiple memory devices.

[0057] Any of the functions or operations described herein can be processed by one processor or a combination of processors. The one processor or the combination of processors is circuitry performing processing and includes circuitry like an application processor (AP, e.g. a CPU), a communication processor (CP, e.g., a modem), a graphics processing unit (GPU), a neural processing unit (NPU) (e.g., an artificial intelligence (AI) chip), a Wi-Fi chip, a Bluetooth® chip, a global positioning system (GPS) chip, a near field communication (NFC) chip, connectivity chips, a sensor controller, a touch controller, a finger-print sensor controller, a display driver integrated circuit (IC), an audio CODEC chip, a universal serial bus (USB) controller, a camera controller, an image processing IC, microprocessors, microcontrollers, digital signal processors, FPGA, ASIC, a microprocessor unit (MPU), a system on chip (SoC), an IC, or the like. The one processor or the combination of processors executes instructions that can be stored in a memory, such as the operating system, in order to control the overall operation of the device. Also, the one processor or the combination of processors is also capable of executing other processes and programs resident in the memory, such as processes for the disclosure.

[0058] It will be appreciated that various embodiments of the disclosure according to the claims and description in the specification can be realized in the form of hardware, software or a combination of hardware and software.

[0059] Any such software may be stored in non-transitory computer readable storage media. The non-transitory computer readable storage media store one or more computer programs (software modules), the one or more computer programs include computer-executable instructions that, when executed by one or more processors of an electronic device individually or collectively, cause the electronic device to perform a method of the disclosure. Additionally, or alternatively, such software may be a computer program [product] comprising instructions which, when executed by one or more processors of an electronic device individually or collectively, cause the electronic device to perform a method of the disclosure.

[0060] Any such software may be stored in the form of volatile or non-volatile storage such as, for example, a storage device like read only memory (ROM), whether erasable or rewritable or not, or in the form of memory such as, for example, random access memory (RAM), memory chips, device or integrated circuits or on an optically or magnetically readable medium such as, for example, a compact disk (CD), digital versatile disc (DVD), magnetic disk or magnetic tape or the like. It will be appreciated that the storage devices and storage media are various embodiments of non-transitory machine-readable storage that are suitable for storing a computer program or computer programs comprising instructions that, when executed, implement various embodiments of the disclosure. Accordingly, various embodiments of the present disclosure may provide a program comprising code for implementing apparatus or a method as claimed in any one of the claims of this specification and a non-transitory machine-readable storage storing such a program.

[0061] Hereinafter, the determination of priority between A and B in the present disclosure may refer to various actions such as selecting the one having a higher priority based on a predefined priority rule and performing an operation corresponding thereto, or omitting or dropping an operation corresponding to the one having a lower priority.

[0062] Hereinafter, "A or B" as described in the present disclosure may be understood as "A and / or B," which may include A, or B, or both A and B.

[0063] In addition, "at least one of A, B, and C" as described in the present disclosure may be understood to include A, or B, or C, or any combination of A, B, and C.

[0064] In addition, "at least one of A, B, or C" as described in the present disclosure may be understood to include A, or B, or C, or any combination of A, B, and C.

[0065] Furthermore, "A / B" as described in the present disclosure may be understood as "A and / or B," which may include A, or B, or both A and B.

[0066] Furthermore, "A, B" as described in the present disclosure may be understood as "A and / or B," which may include A, or B, or both A and B.

[0067] Furthermore, "A and B" as described in the present disclosure may be understood as "A and / or B," which may include A, or B, or both A and B.

[0068] Furthermore, “if condition A and condition B are satisfied,” as described in the present disclosure, may not be limited to a case where both condition A and condition B are satisfied, but may be understood to include a case where either condition A or condition B is individually satisfied, both condition A and condition B are satisfied, or one or more additional conditions are satisfied in combination.

[0069] Furthermore, throughout this disclosure, ordinal terms such as "first," "second," "third," etc., (and similar qualifiers) are used merely to distinguish between different instances, occurrences, configurations, messages, stages, elements or aspects of elements, operations, or information as described herein. Unless the context clearly dictates otherwise, the use of such ordinal terms does not itself require that the elements, operations, or information distinguished by these terms be structurally different, numerically distinct, or substantively dissimilar. For example, a "first signal" and a "second signal" may refer to instances of the same signal transmitted at different times or containing the same core information despite minor variations, or they may refer to signals with different content or characteristics, depending on the specific context. Similarly, a "first value" and a "second value" may represent the same magnitude but measured or applied in different circumstances, or they may represent different magnitudes. The interpretation should be guided by the specific technical context, function, and relationship described in the relevant portion of the specification and claims.

[0070] Furthermore, the terms “first ~”, “second ~”, etc., as described in the present disclosure with respect to various elements (e.g., information, objects, operation, sequences, or the like), should not limit those elements. These terms may only be intended to distinguish one element from another, and may not be intended to indicate a specific order. For example, a first element could be termed a second element, and, similarly, a second element could be termed a first element.

[0071] Furthermore, even if “first ~” and “second ~” are described in the present disclosure, it may be understood that element(s) referred to by “first ~” and “second ~” may be the same or different. For example, in case of element(s) being information, first information and second information may both be same information and, in some cases, are separate and different information.

[0072] In addition, the terms “if ~” and “in case that ~” as used in the disclosure or claims may be interpreted to include the meanings of “when (or upon) ~,” “in response to ~,” “based on ~,” or “according to ~,” and may be used interchangeably with these expressions. In addition, expressions other than those exemplified herein may also be used, as long as they have substantially the same meaning and do not impair the technical features of the present disclosure. If a method step (e.g. transmit a signal) is performed according to the disclosure of the application in connection with one of the above terms (such as “in case that ~” or the like), it may be interpreted to include the meanings (disclosure) of a prior determination that a feature has a specific state “~” (e.g. a bit length is above X), and then perform the method step in response to said determination.

[0073] For example, the physical layer signaling may be referred to as Layer 1 (L1) signaling and may include downlink control information (DCI). In addition, the higher layer signaling may include a medium access control (MAC) control message, a radio resource control (RRC) signaling message, a non-access stratum (NAS) signaling message, or an application layer message. The RRC signaling message may be referred to as L3 (layer 3) signaling. It should be noted, however, that the higher layer signaling is not limited to the aforementioned examples.

[0074] In addition, the term "not perform" as used in the present disclosure or claims may, in context, be understood to mean that the corresponding step is omitted or skipped. Such a term may be replaced with other terms having the same or substantially equivalent meaning.

[0075] In addition, "transmitting a message including A and B" as described in the present disclosure, may be understood as encompassing both (i) transmitting A and B in a single message, and (ii) transmitting A and B separately via multiple messages (e.g., transmitting a first message including A and a second message including B). This interpretation may also apply to messages that include two or more items (e.g., A, B, C), transmitted either together or separately.

[0076] In addition, "transmitting a message including A and transmitting a message including B" may also be interpreted as transmitting a message including A and B in a single message.

[0077] In the embodiments of the present disclosure described herein, terms or components included in the disclosure may be expressed in singular or plural form depending on the specific embodiments presented. However, such singular or plural expressions are selected appropriately for convenience of description, and the present disclosure is not limited to a singular or plural number of components. A component expressed in the plural form may be implemented as a single component, and a component expressed in the singular form may be implemented as multiple components.

[0078] The drawings or flowcharts described herein illustrate example methods that may be implemented according to the principles of the present disclosure, and various modifications may be made to the methods illustrated in the flowcharts of the present disclosure. For example, although illustrated as a series of steps, various steps in each drawing or flowchart may overlap, occur in parallel, occur in a different order, or be repeated. In other examples, any step may be omitted or replaced with another step.

[0079] The process of the flowchart may be performed by a device. One or more of the steps of the flowchart can be implemented by one or more processors / computer programs executing instructions to perform the noted functions.

[0080] The methods and apparatuses proposed in the embodiments of the present disclosure may be disclosed in connection with drawings disclosing flowcharts to illustrate example methods that may be implemented according to the principles of the present disclosure. Such flowcharts may contain different branches and / or sub-branches. It is understood that the principles of the present disclosure do not only contain the combination of all branches / sub-branches disclosed in the embodiment, but the present disclosure also contains at least one isolated branch / isolated sub-branch, in particular to a single branch / single sub-branch.

[0081] The methods and apparatuses proposed in the embodiments of the present disclosure are not limited to each embodiment individually, but may also be applied in combination of all or some of the embodiments proposed in the disclosure. Therefore, the embodiments of the present disclosure may be modified and applied without significantly departing from the scope of the present disclosure, as would be understood by those skilled in the art.

[0082] In this case, even if certain wordings are described differently across embodiments, they may be used interchangeably or in substitution or in combination if their underlying concepts are equivalent. For example, for the same or equivalent concept, even if one embodiment uses the expression "A" and another embodiment uses the expression "B", such expressions may be understood interchangeably, in substitution, or in combination.

[0083] The terms used in the following description to refer to access nodes, network entities, messages, interfaces between network entities, various types of identification information, and the like, are provided merely for the convenience of explanation by way of example. Therefore, the present disclosure is not limited to the terms describedherein, and other terms having equivalent technical meanings may also be used. Such terms may also be interchangeable with terms defined in any 3rd generation partnership project (3GPP) technical specifications (TS) or similar technical specifications, e.g., from the European telecommunications standards institute (ETSI), where appropriate.

[0084] Hereinafter, a base station (BS) is an entity that allocates resources to terminals, and may be at least one of a gNode B, an eNode B, a Node B, a wireless access unit, a BS controller, or a node on a network.

[0085] Furthermore, the base station of the present disclosure may include a split architecture comprising a central unit (CU) and a distributed unit (DU). In this structure, the CU is configured to process the higher layers of the control and user planes, while the DU is configured to process lower-layer radio resource functions. The embodiments of the present disclosure may be equally applicable to 5th generation (5G) base station architectures in which such CU and DU functional splits are implemented.

[0086] A terminal may include a user equipment (UE), a mobile station (MS), a cellular phone, a smartphone, a computer, a tablet, a wearable device, an Internet of Things (IoT) device, or any other device / system capable of performing communication functions.

[0087] In the disclosure, a downlink (DL) refers to a radio link through which a BS transmits a signal to a terminal, and an uplink (UL) refers to a radio link through which a terminal transmits a signal to a BS.

[0088] Furthermore, hereinafter, 5G mobile communication technologies (e.g., 5G new radio (NR)), 6th generation (6G) mobile communication technologies may be described by way of example, but the embodiments of the present disclosure may also be applied to other communication systems having similar technical backgrounds or channel types. For example, newly evolved mobile communication systems developed after 5G and 6G may be included. Furthermore, based on determinations by those skilled in the art, the embodiments of the present disclosure may also be applied to other communication systems (e.g., Wi-Fi systems) through some modifications without significantly departing from the scope of the present disclosure

[0089] In the following description, the terms physical channel and signal may be used interchangeably with data or control signal. For example, the term physical downlink shared channel (PDSCH) refers to a physical channel through which data is transmitted, but the term PDSCH may also be used to refer to the data itself. That is, in the present disclosure, the expression "transmit a physical channel" may be interpreted as being equivalent to the expression "transmit data or a signal via a physical channel."

[0090] Hereinafter, in the context of the present disclosure, higher layer signaling may refer to signaling corresponding to at least one or any combination of the following: master information block (MIB), system information block (SIB) or SIB M (M = 1, 2, ...), RRC, or MAC control element (CE), or a non-access stratum (NAS) signaling message, or an application layer message. The RRC signaling message may be referred to as Layer 3 (L3) signaling.

[0091] In addition, L1 signaling may refer to signaling corresponding to at least one or any combination of signaling techniques using the at least one or any combination of the following physical layer channels or signaling: physical downlink control channel (PDCCH), DCI, UE-specific DCI, group-common DCI, common DCI, scheduling DCI (e.g., DCI used for scheduling downlink or uplink data), non-scheduling DCI (e.g., DCI not used for scheduling downlink or uplink data) physical uplink control channel (PUCCH), or uplink control information (UCI). The L1 signaling message may be referred to as a physical layer signaling.

[0092] Hereinafter, the expression that information is configured by the BS, as used in the present disclosure or claims, may, in context, be understood to mean that the terminal receives the corresponding information from the BS via a physical layer signaling or a higher layer signaling. Such an expression may be replaced with other terms having the same or substantially equivalent meaning.

[0093] Hereinafter, the operational principle of the present disclosure will be described in detail with reference to the accompanying drawings.

[0094] Nowadays more and more active deployment of 5th Generation (5G) New Radio (NR) wireless communication networks takes place, whose advantages and capabilities are broadly known.

[0095] Base stations (BSs) in a 5G NR system use massive antenna arrays (Massive MIMO (mMIMO)) comprising multiple transceiver antenna elements which enable efficient implementation of MIMO ("multiple-input multiple-output") technology, when multiple spatial MIMO layers can be transmitted to transmit data (e.g. physical downlink shared channel (PDSCH)) to one or more user equipments (UEs). A spatial multiplexing (SM) technology enables to use the same frequency and time resources for downlink (DL) transmission of MIMO layers to user equipments, and an adaptive beamforming (BF) technology enables to dynamically steer power of transmitted signal in one or more predetermined directions; orthogonal frequency-division multiplexing (OFDM) modulation provides efficient wideband signal transmission in a multipath channel. Similarly, one or more MIMO layers (e.g. of physical uplink shared channel (PUSCH)) can be transmitted from one or more user equipments to a base station receiver.

[0096] When a user equipment is connecting to a cell served by a base station (e.g. when powering on the user equipment in the cell), an initial access (IA) procedure is performed between the user equipment and the base station. Next, general description of the IA procedure according to 5G NR is provided with reference to the interaction diagram of Fig. 1 and illustrations of Figs. 2-3B.

[0097] A base station periodically broadcasts synchronization signal (SS) / physical broadcast channel (PBCH) blocks (action 0 in Fig. 1), where said broadcast blocks are denoted as SSBs. SSBs are sent by the base station in bursts each including multiple SSBs, and every SSB in a burst has a respective index. Each SSB may be associated with a specific one of spatial beams used by the base station for DL transmission; in other words, appropriate beamforming can be applied with respect to the considered transmission of SSBs. Generally speaking, an SSB is the first signal that is received by the user equipment when connecting to the cell (e.g., as exemplary shown in Fig. 1, by each of the user equipments UEa and UEb which are connecting to the cell).

[0098] Upon having detected an SSB (from which the user equipment becomes aware,inter alia, of an index of the SSB and a physical identifier of the cell), the user equipment, by using the information obtained as a result of decoding system information blocks (SIBs) and according to a predefined rule, determines a time-frequency resource of physical random access channel (PRACH) in which the user equipment can send a random access (RA) preamble. Selection of the PRACH resource generally depends on the SSB index detected by the user equipment.

[0099] Each of the user equipments UEa and UEb randomly selects a RA preamble from a predefined set of RA preambles and performs transmission of the selected RA preamble in the respective PRACH resource (action 1 of Fig. 1). According to 5G NR specification TS 38.213 which is incorporated herein by reference in its entirety, this transmission is denoted as transmission of message Msg1 of the IA procedure. An information about the set or subset of RA preambles from which a user equipment(s) can select a RA preamble is signaled by the base station in a SIB. It should be appreciated that UEa and UEb may select the same RA preamble, due to the random nature of this selection, and accordingly transmit the same RA preamble in Msg1 to the base station. This provides a basis of the collision which is to be resolved in the IA procedure.

[0100] The base station performs demodulation / decoding of the RA preamble from the received PRACH and, based on the results of the RA preamble demodulation / decoding, accordingly generates random access response (RAR) and performs transmission of RAR (action 3 of Fig. 1). According to specification TS 38.213, this transmission is denoted as transmission of message Msg2. The Msg2 transmission is performed in the Medium Access Control (MAC) level (L2) via PDSCH.

[0101] Fig. 2 provides a general exemplary illustration of the RAR structure according to TS 38.213. As can be seen from this figure, the RAR payload includes a timing advance (TA) command for subsequent uplink (UL) transmission, an uplink grant (UL grant), and a temporary identifier (Temp C-RNTI) that is used in the MAC level during random access. R in Fig. 2 denotes a reserved bit(s). According to TS 38.213, the subsequent UL transmission within the IA procedure should be transmission of an RRC setup request from the user equipment via PUSCH, where said transmission is denoted as transmission of message Msg3. That is, the Msg3 transmission is performed in the radio resource control (RRC) level (L3).

[0102] The UL grant in turn includes the following parameters of PUSCH in which Msg3 should be transmitted: a frequency hopping (FH) indication (flag), frequency domain resource allocation (FDRA), time domain resource allocation (TDRA), a modulation and coding scheme (MCS) index, and a transmit power control (TPC) command. According to TS 38.213, there is also a reserved part of the UL grant field.

[0103] In other words, upon having received the RA preamble, the base station schedules subsequent transmission of Msg3 in PUSCH and informs the user equipment about the scheduled PUSCH transmission by means of Msg2 (RAR).

[0104] It should be explained that the TA command signaled within RAR (see Fig. 2) generally represents a value that should, in ideal case, indicate to each user equipment of a plurality of user equipments how earlier the user equipment should perform UL transmission of signals relative to downlink synchronization, so that the UL signals from the plurality of user equipments located at different distances from the base station arrive at the base station almost simultaneously. As a result of the UL signals from different user equipments arriving at the base station simultaneously, the base station can separate them; non-simultaneous arrival of the UL signals at the base station in this case can result in occurrence of mutual interference between signals from different user equipments. In general, the plurality of user equipments are distributed over a service area of the base station, and some user equipments are located near the base station, while some are closer to the cell edge. All other things being equal, an UL signal from a 'nearby' user equipment(s) will arrive at the base station earlier than the one from a 'faraway' user equipment(s); accordingly, the 'faraway' user equipment should transmit its UL signal earlier (i.e. with a greater timing advance) to ensure said simultaneous arrival.

[0105] In 5G NR, the base station measures a TA based on the detection of the RA preamble in the received PRACH (action 2 of Fig. 1). In fact, the base station signals a TA command within RAR as index TA (where TA= 0, 1, ..., 3846), based on which an absolute value TTAis calculated in the user equipment side according to expressions (1) and (2), where TTAdefines the advance of the beginning of transmission of an uplink frame relative to a downlink frame received in the user equipment (see the illustration of Fig. 3A):

[0106] (1),

[0107] where

[0108] (2);

[0109] is a parameter configured for a user equipment(s) by using a SIB;Tcis a constant equal toTc= 1 / 480 kHz / 4096 = 0.509 ns; μ is a subcarrier spacing index (SCS) (where μ = 0, 1, 2, 3, 4, 5, 6) transmitted in the master information block (MIB) in PBCH.

[0110] Fig. 3B illustrates the MAC structure of the RAR payload according to 5G NR, in the standard notation format for a bit structure in octets. As can be seen from Fig. 3B, the TA command occupies 12 bits.

[0111] In case a collision occurs due to transmission of the same RA preamble in the PRACH resource by two or more different user equipments (e.g. UEa and UEb in Fig. 1), the base station may not distinguish between these two or more UL transmissions and may consider that a kind of a composite channel with one RA preamble from some one user equipment has been transmitted. Accordingly, in this case the base station will estimate a TA on this composite channel, and the estimated TA will be the same for said two or more user equipments, regardless of their location in the cell; similarly, the other RAR parameters shown in Fig. 2 will also be the same.

[0112] The user equipment demodulates / decodes the received RAR and obtains therefrom respective information based on which the user equipment performs transmission of Msg3 in PUSCH to the base station (action 4 in Fig. 1). The user equipment signals additional parameters within Msg3, including its respective unique identifier (ID).

[0113] The base station, in general, performs demodulation / decoding of Msg3 received from the user equipment (action 5 in Fig. 1), and, in case the demodulation / decoding is successful, the base station, in accordance with TS 38.213, transmits a collision resolution (Contention Resolution) message in PDSCH, where said transmission is denoted as transmission of message Msg4 (action 6 of Fig. 1). Moreover, the user equipment ID decoded by the base station from Msg3 is included,inter alia, into Msg4. If it is determined in the user equipment that its unique ID matches the ID obtained by the user equipment from the received Msg4, then this will be indicative of successful completion of the IA procedure for the user equipment.

[0114] In accordance with 5G NR, UL channel estimation should be performed in the base station to demodulate / decode PUSCH (Msg3); the channel estimation is performed based on demodulation reference signals (DMRSs) transmitted jointly with PUSCH. In a similar way, DL channel estimation is performed in the user equipment side based on DMRSs transmitted in PDSCH to demodulate / decode PDSCH (Msg4).

[0115] As noted earlier, 5G NR supports multiplexed simultaneous data transmission in multiple MIMO layers in the same system bandwidth (BW) both for DL and UL. Furthermore, the single-user MIMO (SU-MIMO) mode is supported when, for example, all of the MIMO layers multiplexed in PDSCH are intended for one user equipment, and the multi-user (MU-MIMO) MIMO mode is supported when, accordingly, the MIMO layers transmitted in PDSCH are intended for several user equipments.

[0116] A separate DMRS port is associated with each MIMO layer. When DL transmission of data is performed in multiple (N > 1) MIMO layers in PDSCH, a DMRS (DMRS sequence) of a respective DMRS port is transmitted for each of the N MIMO layers in PDSCH. A user equipment(s) uses the N DMRSs received in PDSCH for independent DL channel estimation in each of the respective N DMRS layers and, based on the channel estimation, demodulates / decodes data of these respective MIMO layers. In general, a similar mechanism is also used in 5G NR in multiplexed data transmission in multiple MIMO layers in PUSCH; in particular, in the MU-MIMO mode of multiplexed UL data transmission, orthogonal DMRS sequences transmitted in PUSCH enable to perform, in the base station, respective UL channel estimation per each of the user equipments, i.e., in the MU-MIMO mode, different DMRS ports are used so that the base station is able to estimate UL channels from different user equipments. A unique DMRS port index and a modulating DMRS sequence are associated with every DMRS port in the 5G NR system.

[0117] In 5G NR specification TS 38.211, which is incorporated herein by reference in its entirety, two DMRS patterns are defined, i.e. Type 1 DMRS pattern and Type 2 DMRS pattern.

[0118] Type 1 DMRS pattern is defined by two Code Division Multiplexing (CDM) groups each defining subcarriers in the frequency domain (FD) and OFDM symbols in the time domain (TD) (or, in other words, resource elements (REs) in the time-frequency grid) in which transmission of DMRSs is to be performed, as well as by two orthogonal coverage codes (OCCs) in the frequency domain (FD-OCCs) and two OCCs in the time domain (TD-OCCs). As a result, orthogonal multiplexing of up to eight DMRSs is provided by Type 1 DMRS pattern by using up to two FD-OCCs and up to two TD-OCCs for each of the two CDM groups. Therefore, the DMRS port is generally defined by one CDM group, one FD-OCC code sequence from a predefined plurality thereof, and one TD-OCC code sequence from a predefined plurality thereof. The CDM groups (with indices = 0, 1) of Type 1 DMRS pattern are illustrated in Fig. 4A. It should be noticed that each FD-OCC from said plurality thereof and each TD-OCC from said plurality thereof also has a respective unique index.

[0119] Type 2 DMRS pattern is defined by three CDM groups, as well as by two FD-OCCs and two TD-OCCs. As a result, orthogonal multiplexing of up to twelve DMRS sequences is provided by Type 2 DMRS pattern by using up to two FD-OCCs and up to two TD-OCCs for each of the three CDM groups. Accordingly, transmission of up to 12 MIMO layers can be provided by using Type 2 DMRS pattern. The CDM groups (with indices = 0, 1, 2) of Type 2 DMRS pattern are illustrated in Fig. 4B.

[0120] In accordance with 5G NR specification TS 38.214 (see Section　6.2.2), which is included herein in its entirely by reference, for Msg3 transmission, though it is performed in PUSCH which is a shared channel, the same DMRS port with index 0 is always used, i.e. all user equipments use the same DMRS sequence for this transmission, which is equivalent to the SU-MIMO mode of PUSCH transmission. As follows from the aforesaid, in contrast, in UL data transmission in the normal mode (i.e. when all connections are established), the base station can independently receive data in different MIMO layers from several user equipments in the same BW, and different DMRS ports having different DMRS sequences corresponding thereto are used to this end.

[0121] Since, according to 5G NR, the same DMRS port is always used for transmission of Msg3, the base station will in principle not be able to estimate an individual channel at simultaneous UL transmission of signals from several user equipments, i.e. the base station will substantially estimate the composite UL channel, which makes it difficult to demodulate / decode Msg3 in the base station side. In particular, if there is a collision when the IA procedure is performed (e.g. due to simultaneous UL transmission of Msg3 from UEa and UEb of Fig. 1, which previously selected the same RA preamble), it will be very difficult for the base station to decode these simultaneous transmissions due to degradation in the quality of estimation performed on the composite channel. If the base station is able to correctly decode one of Msg3s (e.g. the one transmitted by the user equipment UEa) and, accordingly, determine its ID, the base station will responsively transmit one Msg4 which will include the ID of UEa. Hence, upon having received this Msg4, UEa will get the confirmation of successful completion of the IA procedure initiated thereby, and UEb, having identified mismatch between its ID and the ID from Msg4, will be obliged to restart the IA procedure. Therefore, the collision between UEa and UEb when performing the IA procedure will be resolved by means of Msg4 in favor of UEa, which will correspond to one scenario of resolving the considered collision. If, for the reasons described above, the base station is unable to correctly decode any of Msg3s transmitted by UEa and UEb, then both user equipments will restart performing the IA procedure, which will correspond to another collision resolution scenario. The situation of the possible collision occurrence discussed above is illustrated by the cross in Fig. 1. It should be noted that, in existing 5G NR systems, the likelihood of unsuccessful decoding of PUSCH during IA due to the abovementioned collision between several user equipments (and, accordingly, roll-back to the beginning of the IA procedure) is not low.

[0122] Although deployment of 5G NR systems in the world is only spinning up, active researches are being already carried out now in different directions for standardization of next generation wireless communication systems, so called 6G, which will have characteristics superior to 5G NR.

[0123] In particular, for the 6G operating range of 7-13 GHz (UPPER MID BAND), it is planned to support, in base stations, extremely large antenna arrays (for instance, comprised of 3072 antenna elements), with hybrid analog and digital beamforming with a large number of antenna ports (≤ 256) and with support for a larger spatial beam directionality. Thus, by supporting, in particular, up to 64 simultaneously transmitted spatial MIMO layers in UPPER MID BAND communication systems, the concept of radio interface with extremely large antenna array (xMIMO) will be rendered to a principally new level, primarily in terms of supporting the advantages of the MU-MIMO mode for DL and UL. Support of the set of reference signals similar to the ones used in 5G NR, such as DMRS, CSI-RS, SRS, PT-RS, PSS / SSS, is planned in 6G. At the same time, the negative effects caused by collisions during IA, as described above with respect to 5G NR, may be of more substantial nature with respect to system performance in the case of 6G.

[0124] Hereinafter reference is made to exemplary embodiments of the present invention, which are illustrated in the accompanying drawings where the same reference numerals denote similar elements. It should be understood that the embodiments of the invention can have various forms and should not be considered to be limited by the descriptions given herein. Therefore, the exemplary embodiments are described hereinbelow with reference to the figures of drawings to elucidate the essence of the aspects of the present invention.

[0125] Fig. 5 generally illustrates a wireless communication system in which different aspects of the present invention can be implemented. As shown in Fig. 5, user equipments (UEs) 501 communicate with base stations (BSs) 502 in a radio access network (RAN) 500. The UEs 501 (e.g., UE 501-1, 501-2, 501-3, ...) are distributed over the RAN 500, and each of the UEs 501 can be stationary or mobile. Broadly known examples of UEs are smartphones, tablets, modems, etc.

[0126] The base stations 502 (e.g., BS 502-A, 502-B, 502-C) are able to provide coverage for a specific geographical area commonly referred to as 'cell.' The base stations 502 basically have a stationary structure, but they can have mobile implementation as well. In general, the base stations can represent macro base stations (as illustrated by the BSs 502-A, 502-B, 502-C in Fig. 5), and pico base stations for pico-cells or femto base stations for femto-cells as well. The cells in turn can be divided into sectors.

[0127] Coordination and management of operating the base stations 502 can be provided by a network controller which is in communication therewith (e.g. via a backhaul connection). The RAN 500 may communicate with a core network (CN) (e.g. via the network controller), which provides various network functions, such as, e.g., access and mobility management, session management, authentication server function, application function, etc. At the same time, the base stations 502 in the RAN 500 can also connect to each other, e.g., via a direct physical connection, which is preferably a high-speed connection.

[0128] When a user equipment is moving within the RAN 500, handover thereof from one base station to another base station can be performed. For example, the UE 501-3 can be handed over from the BS 502-B to the BS 502-A. While performing this, respective communication system parameters are reconfigured in the user equipment for operation with the new base station. The user equipment can be also handed over between sectors of one base station.

[0129] Each of the BSs 502 shown in Fig. 5 includes hardware and logical means to implement respective functions in the base station. The hardware means refer to, in particular, an antenna array, various specially configured processors, controllers, data storage devices, other circuit elements, as well as buses connecting them. The logical means refer to software which is stored in respective memory devices and configures respective circuit elements. Firmware directly hardwired in processors and controllers also refers to the software. The above hardware means are configured inter alia to perform various processing with respect to transmitted and received signals, including (de)modulation, (de)multiplexing, (de)coding, amplifying, filtering, digitizing, (de)interleaving, resource allocation, reception / transmission scheduling.

[0130] In a similar way, each of the UEs 501 shown in Fig. 5 includes hardware and logical means to implement respective functions in the user equipment. The hardware means refer to, in particular, transceiving units with respective antenna elements, various specially configured processor(s), controllers, data storage devices, other circuit elements, as well as buses connecting them. The logical means refer to software which is stored in respective memory devices and configures respective circuit elements. Firmware directly hardwired in controllers also refers to the software. The abovementioned hardware means are configured inter alia to perform various processing with respect to transmitted and received signals, including (de)modulation, (de)multiplexing, (de)coding, amplifying, filtering, digitizing, (de)interleaving. Moreover, the UE comprises means to interact with a user, including a touch screen, speakers / microphone, buttons, as well as user applications which are stored in the memory of the user equipment and executed by the processor of the user equipment in a respective operating system.

[0131] Examples of the abovementioned processors / controllers include microprocessors, microcontrollers, digital signal processors (DSPs), field programmable gate arrays (FPGAs), discrete hardware integrated circuits, etc. Firmware / software executed by the processors / controllers should be construed broadly, as referring to computer-executable instructions, instruction sets, program code, code segments, subroutines, program modules, objects, procedures, etc. The software is stored in respective computer-readable media, which can be implemented, e.g., in the form of random-access memory (RAM), read-only memory (ROM), electrically erasable programmable (EEPROM), solid state storage devices, magnetic storage devices, optical storage devices, etc., which can be recorded or stored with respective program codes and data structures that can be accessed by respective processors / controllers.

[0132] The above-listed hardware and software elements of the base stations and the user equipments are configured to provide execution, in the base stations and in the user equipments, of operations according to the present application, which are described below. Implementation of the component hardware of the base stations and user equipments itself and specialized configuring thereof, including by means of respective logical means, are known in the technical field which the present application relates to. At the same time, various functions consistent with the present application can be executed in a plurality of separate elements or in one or several integral elements, which is defined by design structural characteristics.

[0133] As noted earlier, the present invention is generally aimed at improving the IA procedure by involving the MU-MIMO technology, with signaling from the base station to user equipments which perform the IA procedure about the possibility of selection from a plurality of DMRS ports for UL transmission of Msg3. It should be recalled here that, in accordance with the aforesaid, in 5G NR all user equipments performing IA should use only one DMRS port with index 0 for transmission of Msg3 by default, i.e., in fact, the SU-MIMO mode.

[0134] The IA procedure according to embodiments of the present invention is described hereinafter with reference to the flowchart of the method 600 according to Fig. 6, to the interaction schemes according to Figs. 7, 11 and the illustration of Fig. 8, having the format similar to Figs. 1, 2, respectively, as well as to Figs. 9-10.

[0135] The base station periodically broadcasts SS / PBCH blocks (SSBs) (action 0 in Fig. 7).

[0136] Each of the user equipments UEa and UEb shown in Fig. 7, which are performing the IA procedure, randomly selects an RA preamble from a predefined set of RA preambles and performs transmission of the selected RA preamble (Msg1) in a PRACH resource selected by the user equipment taking into account an index of a SSB detected by the user equipment (step 610 of Fig. 6; action 1 of Fig. 7). As noted earlier, UEa and UEb may select the same RA preamble due to the random nature of this selection, and accordingly transmit the same RA preamble in Msg1s to the base station.

[0137] The base station receives PRACH and measures a TA based on detection of the RA preambles in the received PRACH (action 2 of Fig. 7).

[0138] It should be noted that implementation of actions 0-2 of Fig. 7 and step 610 in the embodiment under consideration generally corresponds to implementation of actions 0-2 of Fig. 1 according to 5G NR described above.

[0139] Based on the results of demodulation / decoding of the RA preambles, the base station generates RAR (step 620 of Fig. 6) and performs transmission of RAR (Msg2) by means of PDSCH (step 630 of Fig. 6; action 3 of Fig. 7).

[0140] Fig. 8, in a format similar to Fig. 2, shows the general schematic illustration of the RAR structure according to the considered preferred embodiment of the present invention. As in 5G NR, the RAR payload includes a TA command, UL grant, and Temp C-RNTI for subsequent PUSCH transmission; UL grant in turn includes the following PUSCH parameters: a FH flag, time-frequency allocation (FDRA / TDRA) information, a MCS index, and TPC. In accordance with one, preferred embodiment, in step 620, DMRS configuration information for UL (DMRS Config) is also included into UL grant within RAR. Alternatively, the reserved part of the UL grant field can be used for the DMRS configuration information (see Figs. 2, 8).

[0141] In accordance with the preferred implementation, a bit value is used to represent the DMRS configuration information within RAR, where said bit value is accordingly selected in the base station from a predefined set of bit values; such a set of bit values can be defined in the specification, or can be preset in the base station and signaled in advance from the base station to a user equipment, e.g. in the MIB or SIBx (where x is a SIB number). As a generalized example, the set of bit values comprises one bit value prescribing to use one DMRS port for PUSCH transmission, which corresponds to the abovementioned SU-MIMO mode of PUSCH transmission (Msg3) according to 5G NR, as well as at least one value respectively indicating more than one DMRS port for selection by a user equipment(s), which corresponds to the MU-MIMO mode of PUSCH transmission according to the present invention. More detailed description of examples of representation of DMRS Config within RAR according to the preferred implementation under consideration is provided hereinbelow.

[0142] Selection of a specific bit value for DMRS Config can be performed in the base station based on, at least, hypotheses regarding a RA preamble or preambles in the received PRACH. For example, if the base station has detected several RA preambles in PRACH (e.g. each of the RA preambles transmitted by UEa and UEb in step 610), the base station in step 620 can select a DMRS Config bit value indicating more than one UL DMRS port to use the MU-MIMO mode to transmit Msg3 in PUSCH from user equipments. As another example, if the base station has detected one RA preamble in PRACH, but the base station has estimated that the likelihood of the fact that this detection is caused by selection of the same RA preamble by different user equipments (e.g. UEa and UEb) - i.e. the detection was performed on the composite channel - exceeds a predefined value, then the base station can again select the DMRS Config bit value indicating more than one UL DMRS port. Said estimation can be based e.g. on delay and / or spatial spread of the composite channel calculated by the base station based on the RA preamble received in PRACH; in particular, if the calculated channel spread is relatively large, then there is a certain likelihood that the transmission was performed from several user equipments. Otherwise, the base station can select the DMRS Config bit value indicating one DMRS port and, accordingly, the 5G NR SU-MIMO mode.

[0143] The user equipment receives Msg2 from the base station, obtains the DMRS Config bit value from UL grant in the received Msg2, and selects a DMRS port according to the received bit value (step 640 of Fig. 6; action 4 of Fig. 7) for subsequent transmission of Msg3 in PUSCH.

[0144] According to one implementation, the DMRS patterns according to 5G NR can be reused for PUSCH transmission in the present invention; more specifically, a DMRS pattern based on 5G NR Type 1 DMRS pattern can be used (see Fig. 4A). Fig. 9A shows the example of such a DMRS pattern for using two DMRS ports - said pattern is defined by two ( = 0, 1) CDM groups and one FD-OCC (e.g. the first one (i.e. having the least index)). Accordingly, when such a DMRS pattern is utilized, the DMRS Config field having length of one bit can be used in RAR.

[0145] Table 1 below illustrates an example of the set of DMRS Config bit values when using the UL DMRS pattern of Fig. 9A.

[0146]

[0147] Table 1

[0148] Accordingly, if in step 620 the base station selects the value '0' for DMRS Config for being included into Msg2, then each of the user equipments, upon having determined this bit value from the received Msg2, will use the same DMRS port for SU-MIMO transmission of Msg3; furthermore, the combination of the first ( =0) CDM group and the first FD-OCC will correspond to the DMRS port with the index 0. If in step 620 the base station selects the value '1' for DMRS Config, then the user equipment will select a DMRS port to be used for MU-MIMO PUSCH transmission (Msg3) from two DMRS ports; accordingly, the combination of the second ( =1) CDM group and the same first FD-OCC will correspond to the other of the DMRS ports.

[0149] In order to enable user equipments to select from a larger number of DMRS ports for PUSCH transmission, a DMRS pattern can be used which is also based on 5G NR Type 1 DMRS pattern and the example of which is shown in Fig. 9B. In accordance with Fig. 9B, this DMRS pattern enables to use up to four DMRS ports and is accordingly defined by two CDM groups ( = 0, 1) and two (the first and second) FD-OCCs. When said DMRS pattern is utilized, the DMRS Config field having length of one or two bits can be used in RAR.

[0150] Table 2 below illustrates an example of the set of DMRS Config bit values when using the UL DMRS pattern of Fig. 9A and the two-bit field.

[0151]

[0152] Table 2

[0153] If in step 620 the base station selects the value '00' for DMRS Config for being included into Msg2, then each of the user equipments will use the same DMRS port 0 for SU-MIMO transmission of Msg3; moreover, the combination of the first CDM group and the first FD-OCC will correspond to the DMRS port with index 0. If the base station selects the value '01' for DMRS Config, then the user equipment will select a DMRS port to be used for MU-MIMO PUSCH transmission from two DMRS ports; accordingly, the combination of the second ( =1) CDM group and the first FD-OCC can correspond to the other of the two DMRS ports. If the base station selects the value '10' for DMRS Config in step 620, then the user equipment will select a DMRS port from four DMRS ports which will have respective combinations of the first and second CDM groups and the first and second FD-OCCs corresponding thereto. As noted earlier, each of the DMRS ports have a different DMRS sequence corresponding thereto which is transmitted in PUSCH.

[0154] Although the DMRS pattern shown in Fig. 9B enables user equipments to select from a larger number of DMRS ports and, accordingly, to implement the MU-MIMO technology for transmission of Msg3 in PUSCH more efficiently, the following problem is typical to this pattern. As follows from the aforesaid and from the illustration of Fig. 9B, the following two mechanisms are substantially used in order to generate four orthogonal DMRS sequences corresponding to four UL DMRS ports: frequency division into two CDM groups and code division in the frequency domain, when two different orthogonal cover code sequences are used on the same subcarriers (FD-OCCs). The problem is caused by the fact that robustness of code division in the frequency domain is relatively low owing to presence of the timing error that results in phase progression in frequency, which disturbs DMRS orthogonality. The disturbance of orthogonality in turn results in mutual interference in DMRSs, which causes degradation of accuracy of UL channel estimation in the base station side.

[0155] Accordingly, motivation in the considered context is to provide a DMRS pattern for UL where usage of code division in the frequency domain is avoided. According to another implementation that corresponds to the embodiment of the present invention, a new DMRS pattern for PUSCH transmission is provided, and the example of the new DMRS pattern is illustrated in Fig. 9C. Said DMRS pattern is defined by four ( = 0, 1, 2, 3) CDM groups and one (e.g. the first) FD-OCC, and, hence, it enables to use four DMRS ports. When said pattern is employed, the DMRS Config field having length of one bit can be used in RAR.

[0156] Table 3 below illustrates an example of the set of DMRS Config bit values when using the UL DMRS pattern of Fig. 9C (there can be a similar set of bit values when the UL DMRS pattern of Fig. 9B and a one-bit field are used).

[0157]

[0158] Table 3

[0159] Accordingly, if in step 620 the base station selects the value '0' for DMRS Config for being included into Msg2, then each of the user equipments, as in 5G NR, will use the same DMRS port with index 0 for SU-MIMO transmission of Msg3 (which in this example corresponds to the combination of the first ( =0) CDM group and the first FD-OCC). If in step 620 the base station selects the value '1' for DMRS Config, then the user equipment will select a DMRS port to be used for MU-MIMO PUSCH transmission from four DMRS ports.

[0160] The proposed DMRS pattern, as illustrated in Fig. 9C, on one hand, enables user equipments to select from a larger number of DMRS ports, and, on the other hand, provides proper orthogonality of respective DMRS sequences by using only frequency division.

[0161] It should be noticed that for DL transmission of Msg2 according to the embodiment under consideration, a MAC RAR structure similar to the one shown in Fig. 3B can be used.

[0162] If the user equipment has determined that the bit value of the DMRS Config field in the received Msg2 is equal to '1' in the case of using the DMRS pattern of Figs. 9A or 9C, or is equal to '01' or '10' in the case of using the DMRS pattern of Fig. 9B, then selection of a DMRS port for UL performed by the user equipment in step 640 can be implemented according to the following options in accordance with an implementation of the present invention.

[0163] According to option 1, selection of a DMRS port for PUSCH is performed randomly:

[0164] (3),

[0165] where is an index of the DMRS port to be used for PUSCH transmission (Msg3); rand() is a random selection function; is the total number of DMRS ports for UL configured by the base station for IA; accordingly, {0, 1, ...,Np,max-1} is the set of DMRS port indices from which the random selection is performed.

[0166] Other options of the mechanism of selecting a DMRS port for PUSCH according to the considered implementation of step 640 are based on a predefined rule.

[0167] In particular, in accordance with option 2, selection of a DMRS port for PUSCH is performed by the user equipment based on an index of a SSB detected by the user equipment:

[0168] (4a), or

[0169] (4b),

[0170] where is the index of the SSB detected by the user equipment and associated with the PRACH resource in Msg1; is the number of SSBs per DMRS port defined by expression whereNSSBis the total number of the SSBs; denotes rounding down to the closest integer, denotes rounding up to the closest integer.

[0171] Motivation for using this option is as follows. As noted earlier, for DL transmission of SSBs, beamforming in different directions is used in the base station side to provide an additional gain and to make the transmission spatially directional. As a rule, a specific direction defined by azimuth and elevation (i.e. a specific spatial beam) is associated with each SSB, and UL MU-MIMO processing in the base station side is also based on interference suppression in certain directions. Accordingly, if SSBs with different indices were received by user equipments (e.g. UEa and UEb of Fig. 7), then directions towards these user equipments are different (see the illustration of Fig. 10, where the dotted line symbolically shows the service area of the base station), and, hence, it would be reasonable to involve the MU-MIMO technology to separate said user equipments in UL, along with respectively assigning thereto different DMRS ports for PUSCH according to equation (4a) or (4b).

[0172] At the same time, if the same SSB is detected by different user equipments (i.e. these user equipments are from the same direction), it may be difficult to separate them in UL in the base station side, even when different DMRS ports are selected in said user equipments; therefore, in this case it may be reasonable to instruct the user equipments to use one DMRS port for PUSCH, e.g. by means of transmitting the value '0' / '00' in the RAR DMRS Config field in Msg2 (see Tables 9A-9C).

[0173] According to option 3, selection of a DMRS port for PUSCH is performed by the user equipment based on an identifier of the user equipment:

[0174] (5),

[0175] where UEidis the user equipment identifier. It should be noticed that several different identifiers are assigned to each user equipment in the communication system; therefore, one of them can be used in equation (5) to select a DMRS port.

[0176] Option 4 corresponds to a combination of the approaches according to options 2 and 3 described above.

[0177] It should be appreciated by a skilled artisan that other options can also be used to select a DMRS port for PUSCH in the user equipment side.

[0178] A specific option of the DMRS port selection mechanism can be predefined in the user equipment or signaled in advance (before performing step 640) by the base station to user equipments (e.g. by means of the MIB / SIB or in Msg2).

[0179] In accordance with another embodiment of the present invention, the DMRS configuration information for UL (DMRS Config) is transmitted by the base station not within Msg2, but in at least one SIB (e.g. in SIB1), i.e. in L3 but not in L2, which is illustrated in Fig. 11. In this another (L3-based) embodiment, the base station broadcasts DMRS Config in the SIB to user equipments substantially before the beginning of performing the IA procedure and, accordingly, is unable to dynamically control this procedure, unlike the abovementioned one (L2-based) embodiment where, based on the hypotheses regarding a RA preamble in Msg1, the base station can switch between an indication of SU-MIMO (one DMRS port for PUSCH) and MU-MIMO (several DMRS ports for PUSCH) in RAR (Msg2). That is, in the other embodiment considered herein, the base station can only signal, by broadcasting, in advance to all user equipments that they should use either the SU-MIMO mode or some option of the MU-MIMO mode to transmit Msg3 in PUSCH.

[0180] Furthermore, in the L3-based embodiment the approaches described above with reference to Tables 1-3 regarding step 620 can be used to signal DMRS Config within the SIB. Selection of a DMRS port for UL by the user equipment in step 640 can be implemented according to the options described above with reference to equations (3)-(5), if the DMRS Config bit value in the received SIB is equal to '1' in the case of using the DMRS pattern of Fig. 9A or 9C, or is equal to '01' or '10' in the case of using the DMRS pattern of Fig. 9B.

[0181] In step 650, the user equipment transmits Msg3 in PUSCH using the DMRS port selected in step 640 (i.e. transmits the DMRS sequence of the selected DMRS port in PUSCH) (action 5 of Fig. 7). In accordance with the aforesaid, the user equipment includes,interalia, its ID into Msg3. Alternatively, the user equipment can include into Msg3 its identifier which was used in equation (5) in step 640, while involving the respective option of the selection mechanism. The PUSCH transmission is performed in step 650 with the timing advance calculated by the user equipment in accordance with equations (1), (2) (see Fig. 3A).

[0182] As symbolically shown in Fig. 7, UEa transmits Msg3 using DMRS port 'A' selected by it, and UEb transmits Msg3 using DMRS port 'B' selected by it, i.e., according to this illustration, the MU-MIMO technology is employed in UL.

[0183] In step 660, the base station receives PUSCH and performs demodulation and decoding of Msg3 based on UL channel estimation performed in the base station based on a DMRS sequence(s) in the received PUSCH, the DMRS sequence corresponding to the DMRS port selected in step 640 (action 6 of Fig. 7). In the illustration of using the MU-MIMO technology in step 650, as shown in Fig. 7 (action 5), the likelihood of the fact that, due to said channel estimation, in step 660 the base station will be able to successfully decode (i.e. separate) Msg3s transmitted by UEa and UEb, respectively, in PUSCH in step 650, even if UEa and UEb in step 610 selected and transmitted the same RA preamble in PRACH, significantly increases. Accordingly, the likelihood of successful resolution of the collision and completion of the IA procedure without returning it to the initial step also increases.

[0184] In step 670, the base station transmits message Msg4 in PDSCH (action 7 of Fig. 7), wherein, as in 5G NR, the base station includes into Msg4,inter alia, the ID decoded from Msg3 in step 660. Accordingly, when Msg3s from UEa and the UEb are successfully separated in step 660, the base station will transmit Msg4 in PDSCH for each of UEa and UEb, along with including thereinto the ID of the respective user equipment, thereby indicating successful completion of the IA procedure for UEa and UEb.

[0185] The capability provided by the present invention to use different DMRS ports by different user equipments for Msg3 transmission also enables to improve TA estimation in the base station side.

[0186] As described above, initial determination of the TA is performed in the base station upon detection of the RA preamble from the received PRACH (step 620; action 2 of Fig. 7), wherein, if several user equipments (e.g. UEa and UEb) select the same RA preamble in PRACH (step 610; action 1 of Fig. 7), TA estimation will be performed by the base station on the composite channel, with respectively signaling a single TA value for all of said several user equipments which are indistinguishable for the base station. The capability to distinguish Msg3 from each of the different user equipments (e.g. from UEa and UEb in the illustration of Fig. 7) by the base station due to using the MU-MIMO technology according to the present invention enables to calculate, in the base station in step 670, an updated TA estimation for each of the user equipments, respectively, and to include an indication of this TA update into respective Msg4 transmitted to this user equipment. Execution itself of TA estimation based on detecting Msg3s from different DMRS ports in PUSCH in said embodiment of step 670 can be based on approaches similar to the ones used in step 620 for TA estimation based on detecting the RA preamble.

[0187] According to the first implementation, by analogy with steps 620, 630, the base station in step 670 includes into Msg4 a TA command in the form of indexTAfor calculating by the user equipment (each of UEa and UEb in the considered illustration of Fig. 7) a new, updated value ofTTAto replaceTTAcalculated in step 650 in accordance with Msg2 (see equations (1), (2)). Such a TA command will also occupy 12 bits in PDSCH (see the illustration of Fig. 3A).

[0188] According to the second implementation, the base station in step 670 includes into Msg4 a command to adjust a TA with respect to the TA signaled in Msg2, said command being included into Msg4 as index where 0, 1, ..., 63. Based on this TA adjustment command, the user equipment (each of UEa and UEb in the illustration of Fig. 7) calculatesNTAfor being used in equation (1) as follows:

[0189] (6)

[0190] where is thevalue ofNTAobtained by a user equipment in step 650 according to equation (2); μ is a SCS index. According to the second implementation under consideration, the TA adjustment command will occupy 6 bits in PDSCH, i.e. reduction of bit load onto PDSCH, as compared to the first implementation, is provided. It should be appreciated by a skilled artisan that said TA adjustment in accordance with the second implementation can be either upward or downward.

[0191] Updating of the TA according to the considered embodiment provides improvement of subsequent UL transmissions from the user equipment performed after the IA procedure.

[0192] FIG. 12 is a block diagram of a terminal or user equipment (UE) 1200 according to an embodiment of the disclosure.

[0193] The terminal is an electronic device capable of wireless communication and having various form factors, examples of the terminal may include a UE, a mobile station (MS), a cellular phone, a smartphone, a computer, a tablet, a wearable device, an Internet of Things (IoT) device, or any other device / system capable of performing wireless communication with a base station (BS) and / or another terminal through a wireless channel.

[0194] Referring to FIG. 12, the UE 1200 may include at least one transceiver (hereinafter, referred to as simply “transceiver”) 1201, at least one processor (hereinafter, referred to as simply “processor”) 1202, and at least one memory (hereinafter, referred to as simply “memory”) 1203. According to at least one or a combination of methods corresponding to the embodiments described in the present disclosure, the transceiver 1201, the processor 1202, and the memory 1203 of the UE 1200 may operate. However, components of the UE 1200 are not limited to the example components illustrated in FIG. 12. In another embodiment, the UE 1200 may further include additional components in addition to the above-mentioned components, or some components may be omitted. Further, in some embodiments, any combination of the transceiver 1201, the processor 1202, or the memory 1203 may be integrated in the form of one component.

[0195] The transceiver 1201 may be a communication circuit or communication circuitry that enables the UE 1200 to perform wireless communication with a node or an entity of a network. For example, the transceiver 1201 may enable the UE 1200 to transmit or receive a signal to or from a BS through cellular communication, or to transmit or receive a signal to or from another UE through cellular communication. For example, the transceiver 1201 may support at least one of various cellular communication technologies including 3rd generation (3G), 4th generation (4G), long term evolution (LTE), 5th generation (5G) NR, 6th generation (6G), and various cellular wireless communication technologies supported by the transceiver (1201) may include all subsequent generations of evolved wireless communications.

[0196] According to an embodiment, the UE 1200 may include a plurality of transceivers. For example, in the case of supporting evolved-universal terrestrial radio access-new radio (E-UTRA-NR) dual connectivity (EN-DC), the UE 1200 may include a first transceiver supporting the 4G LTE wireless communication and a second transceiver supporting the 5G NR wireless communication. According to another embodiment, in the case of supporting NR-dual connectivity (NR-DC), the UE 1200 may include a plurality of transceivers supporting the 5G NR wireless communication. According to still another embodiment, in the case of supporting near field wireless communication, the UE 1200 may separately include a transceiver supporting at least one standard in the group of wireless communication protocol standards as defined in the protocol standards for Bluetooth®, wireless local area network (WLAN) network (including institute of electrical and electronics engineers (IEEE) 802.11-2016 standard or its amendments, e.g., 802.11ah, 802.11ad, 802.11ay, 802.11ax, 802.11az, 802.11ba, and 802.11be, without being limited thereto).

[0197] According to an embodiment, the transceiver 1201 may include various circuit structures used to transmit or receive signals to or from a BS through a wireless channel. The signals may include control information and data. For example, the transceiver 1201 may include a radio frequency (RF) transmitter for up-converting and amplifying the frequency of a transmitted signal and an RF receiver for low-noise-amplifying a received signal and down-converting the frequency thereof. The transceiver 1201 may output a signal received through a wireless channel to the processor 1202 and may transmit, through a wireless channel, a signal output from the processor 1202.

[0198] The processor 1202 may control general operations of the UE 1200 according to embodiments of the disclosure. The processor 1202 may be implemented by one or more integrated circuit (or circuitry) (IC) chips and may execute various data processing operations. The processor 1202 may include at least one electric circuit, and may execute instructions (or a program, codes, data, etc.) stored in the memory 1203, individually, collectively or in any combination thereof. Further, the processor 1202 may include a single-core processor or multi-core processor, and may include a processor assembly including a plurality of processing circuits (circuitry) according to a specific implementation scheme.

[0199] The processor 1202 may be electrically, operatively, and / or communicatively coupled to the transceiver 1201 to control the transceiver 1201.

[0200] The processor 1202 may include at least one processor (or processing circuitry), and the at least one processor may perform the following operations individually, collectively or in any combination thereof. For example, the processor 1202 may include a communication processor (CP) configured to control communication operations and an application processor (AP) configured to control execution of an upper layer (for example, an application layer). In a specific embodiment, at least a part of the processor 1202 may be included in one chip (or IC) and the other part of the processor 1202 may be included in another chip (or IC). Otherwise, at least one processor may be included in another component, for example, the transceiver 1201 or the memory 1203.

[0201] The processor 1202 may perform or control or cause an operation of the UE 1200 for executing at least one or a combination of methods according to embodiments of the disclosure. For example, the processor 1202 may control operations of the UE 1200 for processing a downlink signal received from a BS or generating and transmitting an uplink signal to a BS. To this end, the processor 1202 may execute a computer program, codes, or instructions stored in the memory 1203, so as to control other components of the UE 1200 to enable execution of various operations.

[0202] The memory 1203 corresponds to a hardware storage device capable of temporarily or permanently storing information and may include one or more storage media. For example, the memory 1203 may include a memory assembly including one or more storage media. For example, the one or more storage media may include permanent memory, such as a hard drive, flash memory, or read-only memory (ROM), semipermanent memory, such as random access memory (RAM), cache memory, or a combination thereof.

[0203] The memory 1203 may be electrically, operatively, and / or communicatively coupled to the processor 1202 and may be accessed by the processor 1202.

[0204] The memory 1203 may store a computer program, codes, or instructions executable by the processor 1202. According to an embodiment, a computer program, codes, or instructions executable by the processor 1202 may be either stored in a single memory device or separated and distributedly stored in two or more memory devices. By executing the instructions stored in the memory 1203, the processor 1202 may perform various functions according to an embodiment of the disclosure.

[0205] According to an embodiment of the disclosure, operations of the UE 1200 may be caused to be performed based on execution of instructions (or a computer program or codes) stored in the memory 1203 by at least one processor (or processing circuitry) configured to execute the same individually, collectively, or in any combination thereof, based on processing circuitry that is not configured to execute instructions, and / or based on components of processing circuitry that is not configured to execute instructions.

[0206] FIG. 13 is a block diagram of a base station (BS) 1300 according to an embodiment of the disclosure.

[0207] The BS 1300 may perform wireless communication with at least one user equipment (UE) located within the area of the BS 1300 through a wireless channel. The BS 1300 may perform communication with a node or an entity of a network through wired or wireless communication.

[0208] Referring to FIG. 13, the BS 1300 may include at least one transceiver (hereinafter, referred to as simply “transceiver”) 1301, at least one processor (hereinafter, referred to as simply “processor”) 1302, and at least one memory (hereinafter, referred to as simply “memory”) 1303. According to at least one or a combination of methods corresponding to the embodiments described in the present disclosure, the transceiver 1301, the processor 1302, and the memory 1303 of the BS 1300 may operate. However, components of the BS 1300 are not limited to the example components illustrated in FIG. 13. In another embodiment, the BS 1300 may further include additional components in addition to the above-mentioned components, or some components may be omitted. Further, in some embodiments, any combination of the transceiver 1301, the processor 1302, or the memory 1303 may be integrated in the form of one component.

[0209] The transceiver 1301 may be a communication circuit or communication circuitry that enables the BS 1300 to perform wireless communication with a node or an entity of a network. For example, the transceiver 1301 may enable the BS 1300 to transmit or receive a signal to or from the UE X00 through cellular communication, or to transmit or receive a signal to or from another network entity through wireless communication. For example, the transceiver 1301 may support various cellular communication technologies including 3rd generation (3G), 4th generation (4G), long term evolution (LTE), 5th generation (5G) NR, 6th generation (6G), and various cellular wireless communication technologies supported by the transceiver (1301) may include all subsequent generations of evolved wireless communications. According to an embodiment, the transceiver 1301 may include various circuit structures used to transmit or receive signals to or from a UE through a wireless channel. The signals may include control information and data. For example, the transceiver 1301 may include a radio frequency (RF) transmitter for up-converting and amplifying the frequency of a transmitted signal and an RF receiver for low-noise-amplifying a received signal and down-converting the frequency thereof. The transceiver 1301 may output a signal received through a wireless channel to the processor 1302 and may transmit, through a wireless channel, a signal output from the processor 1302.

[0210] Meanwhile, according to an embodiment of the present disclosure, the BS 1300 may perform communication with a node or an entity of a network through wired or wireless communication. For example, the BS 1300 may perform wired or wireless communication with an adjacent BS, or a node or an entity of a core network through a backhaul network. Although not illustrated in FIG. 13, when the BS 1300 performs wired communication, the BS 1300 may further include a separate network interface for wired communication in addition to the transceiver 1301. The network interface may be referred to as network interface circuitry or communication interface circuitry.

[0211] The processor 1302 may control general operations of the BS 1300 according to embodiments of the disclosure. The processor 1302 may be implemented by one or more integrated circuit (or circuitry) (IC) chips and may execute various data processing operations. The processor 1302 may include at least one electric circuit, and may execute instructions (or a program, codes, data, etc.) stored in the memory 1303, individually, collectively or in any combination thereof. Further, the processor 1302 may include a single-core processor or multi-core processor, and may include a processor assembly including a plurality of processing circuits (circuitry) according to a specific implementation scheme.

[0212] The processor 1302 may be electrically, operatively, and / or communicatively coupled to the transceiver 1301 to control the transceiver 1301.

[0213] The processor 1302 may include at least one processor (or processing circuitry), and the at least one processor may perform the following operations individually, collectively or in any combination thereof. In a specific embodiment, at least a part of the processor 1302 may be included in one chip (or IC) and the other part of the processor 1302 may be included in another chip (or IC). Otherwise, at least one processor may be included in another component, for example, the transceiver 1301 or the memory 1303.

[0214] The processor 1302 may perform or control or cause an operation of the BS 1300 for executing at least one or a combination of methods according to embodiments of the disclosure. For example, the processor 1302 may control operations of the BS 1300 for generating and transmitting a downlink signal to a UE or processing an uplink signal received from a UE. Otherwise, the BS 1300 may transmit or receive a signal to or from a neighboring BS, transfer a signal received from a UE to an upper node of the network, or transmit a signal transferred from an upper node of the network to a UE. To this end, the processor 1302 may execute a computer program, codes, or instructions stored in the memory 1303, so as to control other components of the BS 1300 to enable execution of various operations.

[0215] The memory 1303 corresponds to a hardware storage device capable of temporarily or permanently storing information and may include one or more storage media. For example, the memory 1303 may include a memory assembly including one or more storage media. For example, the one or more storage media may include permanent memory, such as a hard drive, flash memory, or read-only memory (ROM), semipermanent memory, such as random access memory (RAM), cache memory, or a combination thereof.

[0216] The memory 1303 may be electrically, operatively, and / or communicatively coupled to the processor 1302 and may be accessed by the processor 1302.

[0217] The memory 1303 may store a computer program, codes, or instructions executable by the processor 1302. According to an embodiment, a computer program, codes, or instructions executable by the processor 1302 may be either stored in a single memory device or separated and distributedly stored in two or more memory devices. By executing the instructions stored in the memory 1303, the processor 1302 may perform various functions according to an embodiment of the disclosure.

[0218] According to an embodiment of the disclosure, operations of the BS 1300 may be caused to be performed based on execution of instructions (or a computer program or codes) stored in the memory 1303 by at least one processor (or processing circuitry) configured to execute the same individually, collectively, or in any combination thereof, based on processing circuitry that is not configured to execute instructions, and / or based on components of processing circuitry that is not configured to execute instructions.

[0219] The UE or the base station may perform various communication procedures related to the control plane or the user plane by cooperating with one or more network entities based on wireless communication. For example, the UE may communicate with a network entity (for example, an Access and Mobility Management Function (AMF), a Session Management Function (SMF), rtc.) via the base station, or the base station may perform at least one communication procedure by directly transmitting and receiving signals to / from, or relaying signals between, the network entities.

[0220] The structure of the above-described network entity will be described in more detail with reference to the drawings.

[0221] FIG. 14 is a block diagram of a network entity 1400 according to an embodiment of the disclosure.

[0222] The network entity 1400 may include an entity (apparatus, device, or server, etc.) that performs one or more network functions (NFs) or a part of a network function constituting a core network (e.g., a 5th generation (5G) core (5GC)) in a communication system. In this case, multiple NFs may be implemented within a single network entity, or a single NF may be distributed and implemented across a plurality of network entities. In addition, when an NF is implemented within the network entity, the NF may be implemented in the form of software, and in such a case, a program for operating the NF may be stored in memory of the network entity 1400.

[0223] A single NF may be implemented by one or more instances, which may be deployed on the same network entity or distributed across multiple network entities to operate. The instance may be a software unit that logically executes a specific network function, and may be implemented in a form that is decoupled from physical hardware resources. Further, one or more NFs may be implemented in the form of one network slice to operate to satisfy specifications required by a particular service.

[0224] The NF may include at least one of an access and mobility management function (AMF), a session management function (SMF), a local session management function (L-SMF), a user plane function (UPF), a local user plane function (L-UPF), a policy control function (PCF), a unified data management (UDM), a unified data repository (UDR), a network exposure function (NEF), a network repository function (NRF), an application function (AF), a network slice selection function (NSSF), a network data analytics function (NWDAF), a network slice admission control function (NSACF), an authentication server function (AUSF), or a data network (DN), etc.

[0225] Referring to FIG. 14, the network entity 1400 may include at least one network interface 1401, at least one processor 1402 (hereinafter, “processor”), and at least one memory 1403 (hereinafter, “memory”). As described above, a NF may be implemented in the form of a physical device such as the network entity 1400, or may be virtualized and executed in the form of an instance. When implemented as an instance, the NF need not necessarily include physical components as illustrated in FIG. 14. In such a case, the instance may be logically represented as comprising one or more logical functional elements.

[0226] According to at least one or a combination of methods corresponding to the embodiments described in the present disclosure, the network interface 1401, the processor 1402, and the memory 1403 of the network entity 1400 may operate. However, components of the network entity 1400 are not limited to the example components illustrated in FIG. 14. In another embodiment, the network entity 1400 may further include additional components in addition to the above-mentioned components, or some components may be omitted. Further, in an embodiment, the network interface 1401, the processor 1402, or the memory 1403 may be integrated in the form of one component.

[0227] The network interface 1401 is a collective term for a transmitter part of the network entity 1400 and a receiver part of the network entity 1400, and may be a communication circuit for transmitting or receiving a signal to or from a user equipment (UE), a base station (BS), or another network entity. Here, the communication circuit may include both a communication circuit for wireless communication and a communication circuit for a wired communication. For example, the network interface 1401 may include a circuit, logic, hardware, etc., configured to exchange a control plane message or a user plane message with a UE, a BS, or other core network entities through wireless communication or wired communication. The network interface 1401 may operate using various protocols (e.g., non-access stratum (NAS) protocol). The network interface 1401 may also be referred to, for convenience of description or depending on implementation, as communication circuitry, network interface circuitry, or a communication interface circuitry.

[0228] The processor 1402 may control general operations of the network entity 1400 according to embodiments of the disclosure. The processor 1402 may be implemented by one or more integrated circuit (or circuitry) (IC) chips and may execute various data processing operations. The processor 1402 may include at least one electric circuit, and may execute instructions (or a program, codes, data, etc.) stored in the memory 1403, individually, collectively or in any combination thereof. Further, the processor 1402 may include a single-core processor or multi-core processor, and may include a processor assembly including a plurality of processing circuits (circuitry) according to a specific implementation scheme. Further, it should be noted that, according to another embodiment, in a case where NF is implemented in the form of an instance, the network function may be not necessarily configured by physical hardware.

[0229] According to an embodiment, the processor 1402 may be electrically, operatively, and / or communicatively coupled to the network interface 1401 to control the network interface 1401.

[0230] The processor 1402 may include at least one processor (or processing circuitry), and the at least one processor may perform the following operations individually, collectively or in any combination thereof. In a specific embodiment, at least a part of the processor 1402 may be included in one chip (or IC) and the other part of the processor 1402 may be included in another chip (or IC). Otherwise, at least one processor may be included in another component, for example, the network interface 1401 or the memory 1403.

[0231] The processor 1402 may perform or control or cause an operation of the network entity 1400 for executing at least one or a combination of methods according to embodiments of the disclosure. For example, the processor 1402 may control operations of the network entity 1400 for exchanging a control plane message or a user plane message with a UE, a BS, or other core network entities through wireless or wired communication, using various protocols (e.g., NAS protocol). To this end, the processor 1402 may execute a computer program, codes, or instructions stored in the memory 1403, so as to control other components of the network entity 1400 to enable execution of various operations.

[0232] The memory 1403 corresponds to a hardware storage device capable of temporarily or permanently storing information and may include one or more storage media. For example, the memory 1403 may include a memory assembly including one or more storage media. For example, the one or more storage media may include permanent memory, such as a hard drive, flash memory, or read-only memory (ROM), semipermanent memory, such as random access memory (RAM), cache memory, or a combination thereof.

[0233] The memory 1403 may be electrically, operatively, and / or communicatively coupled to the processor 1402 and may be accessed by the processor 1402.

[0234] The memory 1403 may store a computer program, codes, or instructions executable by the processor 1402. According to an embodiment, a computer program, codes, or instructions executable by the processor 1402 may be either stored in a single memory device or separated and distributedly stored in two or more memory devices. By executing the instructions stored in the memory 1403, the processor 1402 may perform various functions according to an embodiment of the disclosure.

[0235] According to an embodiment of the disclosure, operations of the network entity 1400 may be caused to be performed based on execution of instructions (or a computer program or codes) stored in the memory 1403 by at least one processor (or processing circuitry) configured to execute the same individually, collectively, or in any combination thereof, based on processing circuitry that is not configured to execute instructions, and / or based on components of processing circuitry that is not configured to execute instructions.

[0236] In one embodiment, a method of performing initial access (IA) in a wireless communication system is provided, the method comprising, in a user equipment (UE): based on demodulation reference signal (DMRS) configuration information for uplink (UL) received from a base station (BS) of the wireless communication system, performing selection of a DMRS port; and performing transmission, to the base station, of a message Msg3 using the selected DMRS port.

[0237] In another embodiment, a method of performing initial access (IA) in a wireless communication system is provided, the method comprising, in a user equipment (UE): based on demodulation reference signal (DMRS) configuration information for uplink (UL) received from a base station (BS) of the wireless communication system, performing selection of a DMRS port; and performing transmission, to the base station, of a message Msg3 using the selected DMRS port.

[0238] In another embodiment, the transmission of the Msg3 is performed in a physical uplink shared channel (PUSCH), wherein the Msg3 includes, at least, an identifier (ID) of the user equipment, wherein a DMRS of the selected DMRS port is transmitted within the PUSCH; the method further comprises, in the base station: demodulating and decoding the Msg3 received from the user equipment, wherein the demodulating and decoding the Msg3 is performed based on UL channel estimation performed in the base station based on the received DMRS of the selected DMRS port, and transmitting a message Msg4 in a physical downlink shared channel (PDSCH), wherein the Msg4 includes, at least, the ID decoded from Msg3.

[0239] In another embodiment, the method further comprising: transmitting, by the base station, the DMRS configuration information, wherein the DMRS configuration information is represented by a bit value, wherein the bit value is accordingly selected in the base station from a predefined set of bit values, wherein each bit value from at least part of the set of bit values indicates, at least, a number of DMRS ports from which the selection of a DMRS port is to be performed, wherein the set of bit values is predefined in the base station and signaled in advance from the base station to the user equipment.

[0240] In another embodiment, wherein at least one DMRS pattern is preset in the communication system, said DMRS pattern being defined by: two or more code division multiplexing (CDM) groups each defining subcarriers and OFDM symbols in which UL transmission of DMRSs is to be performed; and one or more orthogonal cover codes (OCCs) in frequency domain (FD).

[0241] In another embodiment, said DMRS pattern is based on 5G NR Type 1 DMRS pattern and is defined by two CDM groups and two FD-OCCs, or said DMRS pattern is defined by four CDM groups and one FD-OCC.

[0242] In another embodiment, wherein each bit value from said at least part of the set of bit values further indicates a combination of one or more CDM groups and at least one FD-OCC, the combination corresponding to a number of DMRS ports indicated by said bit value.

[0243] In another embodiment, wherein said at least part of the set of bit values comprises: a bit value indicating one DMRS port, and at least one bit value respectively indicating more than one DMRS port; wherein, if a bit value indicates more than one DMRS port, said selection of a DMRS port is performed randomly or based on a predefined rule.

[0244] In another embodiment, wherein the predefined rule for selecting a DMRS port is: (i) based on an index of a synchronization signal (SS) / physical broadcast channel (PBCH) block detected by the user equipment: or , where is a DMRS port index;Np,maxis a total number of DMRS ports for UL configured by the base station for IA; SSBidxis the index of the detected SS / PBCH block (SSB); is a number of SSBs per DMRS port defined by whereNSSBis a total number of SSBs; denotes rounding down to a nearest integer, denotes rounding up to a nearest integer, or (ii) based on the ID of the user equipment included into the Msg3, or (iii) based on a combination of (i) and (ii).

[0245] In another embodiment, the method further comprising, in the base station: receiving, from the user equipment, a message Msg1 with a random access (RA) preamble transmitted by the user equipment in a physical random access channel (PRACH), wherein the RA preamble has been randomly selected by the user equipment from a predetermined plurality of RA preambles; and transmitting a random access response (RAR) message Msg2 in the PDSCH, wherein the Msg2 comprises, at least, frequency domain and time domain resource allocations for the transmission of the Msg3 in the PUSCH.

[0246] In another embodiment, the method further comprising, in the base station: further including into the Msg2 the bit value representing the DMRS configuration information, wherein said selection of a DMRS port is performed using the bit value received in the Msg2 from the base station.

[0247] In another embodiment, wherein said receiving a Msg1 further comprising: receiving, in the PRACH, a Msg1 from each of one or more other user equipments performing IA, wherein selection, by the base station, of the bit value representing the DMRS configuration information for inclusion into the Msg2 is based at least partially on the RA preambles from the received Msg1s.

[0248] In another embodiment, the bit value representing the DMRS configuration information is broadcasted by the base station in one of system information blocks (SIBs) or in a master information block (MIB), wherein said selection of a DMRS port is performed using the bit value received in the SIB or the MIB from the base station.

[0249] In another embodiment, the method further comprising, in the base station: based on detecting the RA preamble in the Msg1, determining a timing advance (TA) for the transmission of the Msg3 in the PUSCH, and further including an indication of the TA into the Msg2; based on detecting the DMRS in the PUSCH, calculating an updated TA, and further including a TA update indication into the Msg4.

[0250] In another embodiment, the TA update indication represents: an indication of a TA adjustment relative to the TA signaled in the Msg2, or an indication of the updated TA to replace the TA signaled in the Msg2.

[0251] In another embodiment, a method of performing initial access (IA) in a wireless communication system is provided, the method comprising: by a base station (BS) of the wireless communication system, generating a random access response (RAR) message Msg2, said generating comprising: including demodulation reference signal (DMRS) configuration information for uplink (UL) into the Msg2, and performing transmission of the Msg2; in a user equipment (UE), based on the DMRS configuration information from the Msg2 received from the base station, performing selection of a DMRS port, and performing transmission, to the base station, of a message Msg3 using the selected DMRS port.

[0252] In another embodiment, wherein the transmission of the Msg2 is performed in a PDSCH, wherein the Msg2 comprises frequency domain and time domain resource allocations for the transmission of the Msg3; the transmission of the Msg3 is performed in a PUSCH, wherein the Msg3 includes, at least, an ID of the user equipment, wherein a DMRS of the selected DMRS port is transmitted within the PUSCH; the method further comprises, in the base station: demodulating and decoding the Msg3 received from the user equipment, wherein the demodulating and decoding the Msg3 is performed based on UL channel estimation performed in the base station based on the received DMRS of the selected DMRS port, and transmitting a message Msg4 in the PDSCH, wherein the Msg4 includes, at least, the ID decoded from the Msg3.

[0253] In another embodiment, said including DMRS configuration information into the Msg2 comprises including into the Msg2 a bit value representing the DMRS configuration information, wherein the bit value is accordingly selected in the base station from a predefined set of bit values, wherein each bit value from at least part of the set of bit values indicates, at least, a number of DMRS ports from which the selection of a DMRS port is to be performed, wherein the set of bit values is predefined in the base station and signaled in advance from the base station to the user equipment; said selection of a DMRS port is performed using the bit value received in the Msg2.

[0254] In another embodiment, at least one DMRS pattern is preset in the communication system, said DMRS pattern being defined by: two or more CDM groups each defining subcarriers and OFDM symbols in which UL transmission of DMRSs is to be performed; and one or more FD-OCCs.

[0255] In another embodiment, said DMRS pattern is based on 5G NR Type 1 DMRS pattern and is defined by two CDM groups and two FD-OCCs, or said DMRS pattern is defined by four CDM groups and one FD-OCC.

[0256] In another embodiment, each bit value from said at least part of the set of bit values further indicates a combination of one or more CDM groups and at least one FD-OCC, the combination corresponding to a number of DMRS ports indicated by said bit value.

[0257] In another embodiment, said at least part of the set of bit values comprises: a bit value indicating one DMRS port, and at least one bit value respectively indicating more than one DMRS port; wherein, if a bit value indicates more than one DMRS port, said selection of a DMRS port is performed randomly or based on a predefined rule.

[0258] In another embodiment, the predefined rule for selecting a DMRS port is: (i) based on an index of an SSB detected by the user equipment: or where is a DMRS port index;Np,maxis a total number of DMRS ports for UL configured by the base station for IA; SSBidxis the index of the detected SSB; is a number of SSBs per DMRS port defined by whereNSSBis a total number of SSBs; denotes rounding down to a nearest integer, denotes rounding up to a nearest integer, or (ii) based on the ID of the user equipment included into the Msg3, or (iii) based on a combination of (i) and (ii).

[0259] In another embodiment, the method further comprising, in the base station: receiving, from the user equipment, a message Msg1 with a RA preamble transmitted by the user equipment in a PRACH, wherein the RA preamble has been randomly selected by the user equipment from a predetermined plurality of RA preambles.

[0260] In another embodiment, said receiving a Msg1 further comprising: receiving, in the PRACH, a Msg1 from each of one or more other user equipments performing IA, wherein selection, by the base station, of the bit value representing the DMRS configuration information for inclusion into the Msg2 is based at least partially on the RA preambles from the received Msg1s.

[0261] In another embodiment, the method further comprising, in the base station: based on detecting the RA preamble in the Msg1, determining a TA for the transmission of the Msg3 in the PUSCH, and further including an indication of the TA into the Msg2; based on detecting the DMRS in the PUSCH, calculating an updated TA, and further including a TA update indication into the Msg4.

[0262] In another embodiment, the TA update indication represents: an indication of a TA adjustment relative to the TA signaled in the Msg2, or an indication of the updated TA to replace the TA signaled in the Msg2.

[0263] In another embodiment, a user equipment (UE) in a wireless communication system is provided, the user equipment comprising, at least: transceiving units; data processing units; and data storage units, wherein the data storage units have computer-executable codes stored therein which, when executed by the data processing units, cause the method according to the embodiments of the disclosure to be performed.

[0264] In another embodiment, a computer-readable storage medium has computer-executable codes stored therein which, when executed by at least one data processing unit of a user equipment (UE), cause the user equipment to perform the method according to the embodiments of the disclosure.

[0265] In another embodiment, a wireless communication system comprises at least a base station (BS), the base station comprising, at least: transceiving units; data processing units; and data storage units, wherein the base station is in communication with at least one user equipment (UE) comprising, at least: transceiving units; data processing units; and data storage units, wherein the data storage units of the base station have computer-executable codes stored therein, and the data storage units of the user equipment have computer-executable codes stored therein, wherein the computer-executable codes, when executed by the data processing units of the base station and the user equipment, cause the method according to the embodiments of the disclosure to be performed.

[0266] The present invention generally provides improvement of the IA procedure for 6G xMIMO systems by flexibly using the MU-MIMO technology. More specifically, the present invention provides, for the IA procedure, reduction of the likelihood of unsuccessful decoding of Msg3 from PUSCH due to the collision between user equipments performing IA, as well as improved accuracy of TA estimation for UL.

[0267] It should also be understood that the illustrated exemplary embodiments are only preferred, but not the only possible embodiments of the present invention. Specifically, the scope of the present invention is defined by the following claims and equivalents thereof.

[0268] Meanwhile, although specific embodiments of the present disclosure have been described in detail, various modifications may be made without departing from the scope of the present disclosure. Therefore, the scope of the present disclosure should not be limited to the described embodiments, but should be defined by the claims and equivalents thereof.

Claims

1.A method of performing initial access (IA) in a wireless communication system performed by a user equipment (UE), the method comprising:based on demodulation reference signal (DMRS) configuration information for uplink (UL) received from a base station (BS) of the wireless communication system, performing selection of a DMRS port; andperforming transmission, to the base station, of a Msg3 using the selected DMRS port.2.The method of claim 1, whereinthe transmission of the Msg3 is performed in a physical uplink shared channel (PUSCH), wherein the Msg3 includes, at least, an identifier (ID) of the user equipment, wherein a DMRS of the selected DMRS port is transmitted within the PUSCH.3.The method of claim 2, further comprising: receiving, from the base station, the DMRS configuration information, wherein the DMRS configuration information is represented by a bit value, wherein the bit value is accordingly selected in the base station from a predefined set of bit values, wherein each bit value from at least part of the set of bit values indicates, at least, a number of DMRS ports from which the selection of a DMRS port is to be performed, wherein the set of bit values is predefined in the base station and signaled in advance from the base station to the user equipment.4.The method of claim 3, wherein at least one DMRS pattern is predefined, and the at least one DMRS pattern is defined by: two or more code division multiplexing (CDM) groups each defining subcarriers and OFDM symbols in which UL transmission of DMRSs is to be performed; and one or more orthogonal cover codes (OCCs) in frequency domain (FD).5.The method of claim 4, whereinthe at least one DMRS pattern is based on 5G NR Type 1 DMRS pattern and is defined by two CDM groups and two FD-OCCs, orthe at least one DMRS pattern is defined by four CDM groups and one FD-OCC.6.The method of claim 5, wherein each bit value from the at least part of the set of bit values further indicates a combination of one or more CDM groups and at least one FD-OCC, the combination corresponding to a number of DMRS ports indicated by the bit value.7.The method of claim 3, wherein the at least part of the set of bit values comprises: a bit value indicating one DMRS port, and at least one bit value respectively indicating more than one DMRS port; wherein, if a bit value indicates more than one DMRS port, the selection of a DMRS port is performed randomly or based on a predefined rule.8.The method of claim 7, wherein the predefined rule for selecting a DMRS port is:(i) based on an index of a synchronization signal (SS) / physical broadcast channel (PBCH) block detected by the user equipment:orwhereis a DMRS port index;Np,maxis a total number of DMRS ports for UL configured by the base station for IA; SSBidxis the index of the detected SS / PBCH block (SSB);is a number of SSBs per DMRS port defined bywhereNSSBis a total number of SSBs;denotes rounding down to a nearest integer,denotes rounding up to a nearest integer, or(ii) based on the ID of the user equipment included into the Msg3, or(iii) based on a combination of (i) and (ii).9.The method of claim 3, further comprising:transmitting, to the base station, a Msg1 with a random access (RA) preamble in a physical random access channel (PRACH), wherein the RA preamble has been randomly selected by the user equipment from a predetermined plurality of RA preambles; andreceiving, from the base station, a random access response (RAR) Msg2 in the PDSCH, wherein the Msg2 comprises, at least, frequency domain and time domain resource allocations for the transmission ofthe Msg3 in the PUSCH.10.The method of claim 9, wherein the selection of a DMRS port is performed using the bit value received in the Msg2 from the base station.11.The method of claim 10, wherein receiving the Msg1 further comprising: receiving, in the PRACH, the Msg1 from each of one or more other user equipments performing IA, wherein selection, by the base station, of the bit value representing the DMRS configuration information for inclusion into the Msg2 is based at least partially on the RA preambles from the received Msg1s.12.The method of claim 9, wherein the bit value representing the DMRS configuration information is broadcasted by the base station in one of system information blocks (SIBs) or in a master information block (MIB), wherein the selection of a DMRS port is performed using the bit value received in the SIB or the MIB from the base station.13.A method of performing initial access (IA) in a wireless communication system performed by a base station (BS), the method comprising:generating a random access response (RAR) message (Msg2), wherein the generating comprising: including demodulation reference signal (DMRS) configuration information for uplink (UL) into the Msg2;transmitting, to a user equipment (UE), the Msg2; andreceiving, from the UE, a Msg3 using a DMRS port selected based on the DMRS configuration information included in the Msg2.14.The method of claim 13, whereinthe Msg2 is transmitted in a PDSCH, wherein the Msg2 comprises frequency domain and time domain resourceallocations for the transmission of the Msg3;the Msg3 is transmitted in a PUSCH, wherein the Msg3 includes, at least, an ID of the user equipment, wherein a DMRS of the selected DMRS port is transmitted within the PUSCH;and wherein the method further comprises:demodulating and decoding the Msg3 received from the user equipment, wherein the demodulating and decoding the Msg3 is performed based on UL channel estimation performed in the base station based on the received DMRS of the selected DMRS port, andtransmitting a Msg4 in the PDSCH, wherein the Msg4 includes, at least, the ID decoded from the Msg3.15.A user equipment (UE) comprising:at least one transceiver;at least one processor communicatively coupled to the at least one transceiver; andat least one memory, communicatively coupled to the at least one processor, storing instructions executable by the at least one processor individually or in any combination to cause the UE to:based on demodulation reference signal (DMRS) configuration information for uplink (UL) received from a base station (BS) of the wireless communication system, perform selection of a DMRS port, andperform transmission, to the base station, of a Msg3 using the selected DMRS port.

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