Methods and apparatus for performing contention resolution RACH less transmissions in a wireless communication system

Abstract

The disclosure relates to a 5G or 6G communication system for supporting higher data transmission rates and satisfying various service requirements. A method performed by a terminal in a wireless communication system comprising: receiving, from a base station, configuration information on transmission resources to be used for an RACH-less transmission; determining a resource among the transmission resources; transmitting, to the base station, a message 3 of a random access procedure based on the resource, the message 3 including uplink data for EDT; and receiving, from the base station, a message 4 of the random access procedure, as a response of the message 3.

Description

METHODS AND APPARATUS FOR PERFORMING CONTENTION RESOLUTION RACH LESS TRANSMISSIONS IN A WIRELESS COMMUNICATION SYSTEM

[0001] The disclosure relates generally to wireless communication system, and more particularly, to methods and apparatus for performing contention-resolution Random Access Channel-less (RACH-less) transmissions in a wireless communication system.

[0002] 5thgeneration (5G) mobile communication technology defines a wide frequency band to enable fast transmission speeds and new services, and can be implemented in a sub-6 gigahertz (GHz) frequency band such as 3.5GHz, and in an ultra-high frequency band, which may be referred to as millimeter wave (mmWave) bands, such as 28GHz and 39GHz (above 6GHz) bands.

[0003] In 6thgeneration (6G) mobile communication technology, which may be referred to as beyond 5G, it is expected that securing new frequency resources such as the sub-6GHz band, ultra-high frequency bands, and upper mid band (7-24GHz) will be important to handle the rapidly increasing data traffic due to the spread of artificial intelligence (AI) technology and increasing streaming services, to improve user perceived performance, and to efficiently utilize all available frequency resources as needed. To this end, reallocation, reuse, or sharing of existing frequency bands from 2ndgeneration (2G) to 5G can be considered for 6G.

[0004] Since the introduction of 5G, the communications market has been increasingly interested in improving system operation efficiency, sustainability, and user experience. Accordingly, in addition to improving traditional communications performance such as data transmission speed and delay time, the introduction of new innovative technologies such as AI, reducing operating costs, improving energy efficiency, expanding service coverage, and introducing new services are becoming increasingly important.

[0005] Since the early stages of 5G mobile communication technology, a goal has been to support services and satisfy performance requirements for enhanced mobile broadband (eMBB), ultra-reliable low-latency communications (URLLC), and massive machine-type communications (mMTC), including beamforming and massive multiple-input multiple-output (MIMO) to mitigate path loss of radio waves in ultra-high frequency bands and increase the range of radio transmission, support for various numerologies (such as operation of multiple subcarrier intervals) and dynamic operation of slot formats for efficient use of ultra-high frequency resources, initial access technology to support multi-beam transmission and wideband, definition and operation of band-width part (BWP), new channel coding methods such as low density parity check (LDPC) codes for large-capacity data transmission and polar codes for reliable transmission of control information, layer 2 (L2) pre-processing, and networks that provide dedicated networks specialized for specific services. Additionally, standardization of slicing (network slicing), etc., has been progressing.

[0006] Discussions have also been held on improving and enhancing the initial 5G mobile communication technology in consideration of the services that 5G mobile communication technology was intended to support, including vehicle-to-everything (V2X) to help autonomous vehicles make decisions based on their own location and status information transmitted by the vehicle and to increase user convenience, new radio unlicensed (NR-U) for system operation that meets various regulatory requirements in unlicensed bands, new radio (NR) terminal low power consumption technology (i.e., UE power saving), non-terrestrial network (NTN), which is direct terminal-satellite communication to secure coverage in areas where communication with terrestrial networks is impossible, positioning, NR support up to 71GHz, support of reduced capability NR devices for lower cost and complexity compared to general terminals, user equipment (UE) power saving enhancement for improved power management in preparation for the use of various terminal types, and sidelink (SL). Standardization of the physical layer has been performed for technologies such as SL enhancement, duplex enhancements which study a new form of duplexing called subband non-overlapping full duplex (SBFD), network energy saving which secures the idle period in which the base station operates in maximum power saving mode to the maximum extent and reduces power consumption, and network controlled repeaters which have improved performance compared to existing repeaters by having the function of receiving and processing side control information from the network.

[0007] In addition, standardization of the wireless interface architecture / protocol layer for technologies such as the industrial Internet of things (IIoT) for supporting new services through linkage and convergence with other industries, integrated access and backhaul (IAB) that provides nodes for expanding network service areas by integrating wireless backhaul links and access links, mobility enhancement technology including conditional handover (CHO) and dual active protocol stack (DAPS) handover, 2-step random access channel (RACH) for NR that simplifies random access procedures, multicast and broadcast, standardization of support for multi universal subscriber identity module (USIM) devices that provide services to users using information of two or more subscriber identity modules (SIMs), SL relay that provides relay-related functions to support connections between terminals in long distances and between terminals and networks, small data transfer (SDT) which transmits small data or signalling in an inactive state without transitioning to a connected state, mobility enhancements including layer 1 (L1) / L2 triggered mobility (LTM) / subsequent conditional PSCell addition / change (SCPAC) / and CHO with candidate secondary cell groups (SCGs), extended reality (XR) enhancement to support XR services in NR systems, etc., has also been performed, and standardization of system architecture / services such as 5G baseline architecture (e.g., service-based architecture, service-based interface) for grafting network functions virtualization (NFV) and software-defined networking (SDN) technologies, mobile edge computing (MEC) that provides services based on the location of the terminal, non-public networks (NPNs) that can be used only by some permitted terminals for non-public purposes, disaster roaming that supports the use of communication services through other carriers' networks in the event of a communication disaster, proximity-based service via 5GS, and unmanned standardization has also been made in the system architecture / service areas, including support of an unmanned aircraft system (UAS) to support remote identification, tracking, and authorization of uncrewed aerial vehicles (UAVs), structural enhancements to support XR and interactive media services, 5GS to support AI / machine learning (ML) services, and advanced MEC to provide edge computing services in roaming networks, etc. has also been performed.

[0008] Currently, standardization is in progress for technologies such as beam prediction using AI / ML technology, channel state information (CSI) prediction to improve positioning accuracy, ultra-low-power terminal technology using low-power wake-up receivers, technology for transmitting long term evolution (LTE) broadcasts to 5G networks, MIMO transmission technology using multiple base stations, and ultra-low-power terminals (e.g., ambient IoT) that transmit data by obtaining power from an external source without a battery.

[0009] At the radio interface architecture / protocol layer, standardization is in progress for technologies such as LTM scenario support and conditional LTM support between central units (CUs), simultaneous support for the same XR service between multiple devices, NTN coverage enhancement and evolution, AI / ML-based mobility support, and terminal-to-terminal connection relay across multiple hops between terminals and networks.

[0010] In addition, standardization of system architecture / service fields for satellite communication optimization methods, 5G system energy usage management and efficiency, SBI-based user plane evolution, ambient IoT technology, data service provision methods in Internet protocol (IP) multimedia subsystem (IMS), and avatar communication service persists. When such 5G mobile communication systems are commercialized, a vast increase in devices connected to the communication network will be realized, and accordingly, it is expected that the functions and performance of 5G mobile communication systems will be strengthened and integrated operation of connected devices will be required. To this end, new research will be additionally conducted on XR to efficiently support augmented reality (AR), virtual reality (VR), and mixed reality (MR), 5G performance improvement and complexity reduction using AI / ML, AI service support, metaverse service support, and drone communication.

[0011] The development of these 5G mobile communication systems is expected to serve as a basis for enhancing 5G performance and ultimately evolving into 6G. In the 6G era, eMBB, URLLC, and mMTC services are expected to evolve into immersive communication (IC), hyper-reliable and low-latency communication (HRLLC), and massive communication (MC) services, respectively. In addition, new services such as AI and communication, integrated sensing and communication, and ubiquitous connectivity are expected to be additionally supported. For these 6G services, improved performance requirements compared to 5G are also essential, and standardization to define these is also in progress.

[0012] In this manner, to satisfy the expanded services and improved performance requirements of 6G, it is expected that it will be beneficial to optimize and improve system operation, such as introducing AI technology, improving energy efficiency, expanding coverage, and applying next-generation security technology, as well as developing sustainable communication technology, in addition to simply improving existing communication performance.

[0013] To this end, the latest AI technology is applied to all areas from the communication system design stage to development, management, and operation to improve communication performance and realize AI internalization technology that realizes network automation and efficiency, technology that improves user-perceived performance and network operation efficiency by improving power consumption of networks and terminals, technology that reduces power consumption in core base station components such as radio frequency (RF) and modems and in the channel coding and signal modulation and transmission / reception processes, multi-antenna transmission technology (e.g., extreme MIMO (X-MIMO)) that utilizes large antennas to overcome propagation path loss due to high frequency compared to the 3.5 GHz band of 5G communication and provide equivalent coverage, transmission / reception technology based on multiple base stations (e.g., distributed MIMO (D-MIMO)) to improve quality in cell edge areas, full-duplex communication (e.g., SBFD) technology to improve frequency efficiency and system network, next-generation encryption technology (e.g., post quantum cryptography (PQC)) and zero trust architecture (ZTA) technology to strengthen 6G communication security, and initial access delay and mobility. Research will be focused on technologies to minimize delay, design a hardware-friendly protocol structure for ultra-high-speed data processing, and expand the application of integrity protection technologies.

[0014] In addition, research will be conducted on the structure of mobile communication systems (prevention of redundant functions, simplification of functions, etc.), introduction of new planes for providing service providers, user privacy protection measures, realistic services, enhancement of network resiliency, network sharing technologies, improved security technologies (false base stations, lower layer protection, etc.), and intent-based network operation and management.

[0015] The above information is presented as background information only to assist with an understanding of the present disclosure. No determination has been made, and no assertion is made, as to whether any of the above might be applicable as prior art with respect to the present invention.

[0016] Random access is a procedure performed by a terminal to connect to a base station in order to receive necessary data or services. To enable rapid data transmission, the terminal may perform early data transmission (EDT) while the random access procedure is in progress. In contention-based random access, the base station may apply diversity slotted aloha (DSA) and perform successive interference cancellation (SIC) to resolve contention.

[0017] The disclosure has been made to address the above-mentioned problems and disadvantages, and to provide at least the advantages described below.

[0018] Accordingly, an aspect of the disclosure is to provide a method and apparatus for handling a data transmission and a contention resolution for random access channel (RACH) less random access procedure.

[0019] Another aspect of the disclosure is to provide a method and an apparatus for determining resources for transmission and / or reception associated with the RACH less random access procedure with EDT and DSA.

[0020] Additional aspects will be set forth in part in the description which follows and, in part, will be apparent from the description, or may be learned by practice of the presented embodiments.

[0021] In accordance with an embodiment of the disclosure, a method performed by a terminal in a wireless communication system is provided and includes: receiving, from a base station, configuration information on transmission resources to be used for a random access channel (RACH)-less transmission; determining a resource among the transmission resources; transmitting, to the base station, a message 3 of a random access procedure based on the resource, the message 3 including uplink data for early data transmission (EDT); and receiving, from the base station, a message 4 of the random access procedure, as a response of the message 3.

[0022] In accordance with an embodiment of the disclosure, a method performed by a base station in a wireless communication system is provided and includes: A method performed by a base station in a wireless communication system, the method comprising: transmitting, to a terminal, configuration information on transmission resources to be used for an RACH-less transmission; receiving, from the terminal, a message 3 of a random access procedure based on a resource among the transmission resources, the message 3 including uplink data for EDT; and transmitting, to the terminal, a message 4 of the random access procedure, as a response of the message 3.

[0023] In accordance with an embodiment of the disclosure, a terminal in a wireless communication system is provided and includes: a transceiver; a processor communicatively coupled to the transceiver; and memory, communicatively coupled to the processor, storing instructions executable by the processor to cause the terminal to: receive, from a base station, configuration information on transmission resources to be used for an RACH-less transmission, determine a resource among the transmission resources transmit, to the base station, a message 3 of a random access procedure based on the resource, the message 3 including uplink data for EDT, and receive, from the base station, a message 4 of the random access procedure, as a response of the message 3.

[0024] In accordance with an embodiment of the disclosure, a base station in a wireless communication system is provided and includes: a transceiver; a processor communicatively coupled to the transceiver; and memory, communicatively coupled to the processor, storing instructions executable by the processor to cause the base station to: transmit, to a terminal, configuration information on transmission resources to be used for an RACH-less transmission, receive, from the terminal, a message 3 of a random access procedure based on a resource among the transmission resources, the message 3 including uplink data for EDT, and transmit, to the terminal, a message 4 of the random access procedure, as a response of the message 3.

[0025] These and other aspects of the embodiments will be better understood with the following description and accompanying drawings. The descriptions, indicating preferred embodiments and specific details, are for illustration and not limitation. Many modifications can be made within the scope of the embodiments, which include all such modifications.

[0026] According to an embodiment of the disclosure, the data transmission delay and signaling overhead can be reduced by allowing early data transmission (EDT) without requiring a complete random access.

[0027] In addition, according to an embodiment of the disclosure, the data transmission reliability and channel resource efficiency can be improved by applying successive interference cancellation (SIC) in contention-based random access using diversity slotted aloha (DSA).

[0028] The effects obtainable in the disclosure are not limited to the above-mentioned effects, and other effects not mentioned herein will be clearly understood from the following description by those skilled in the art to which the disclosure belongs.

[0029] Figure 1 illustrates a non-terrestrial network architecture according to an embodiment of the disclosure.

[0030] Figure 2 illustrates an ephemeris synchronization process according to an embodiment of the disclosure.

[0031] Figure 3 illustrates an initial access procedure according to an embodiment of the disclosure.

[0032] Figure 4 illustrates an early data transmission procedure according to an embodiment of the disclosure.

[0033] Figure 5 illustrates a preconfigured uplink resource procedure according to an embodiment of the disclosure.

[0034] Figure 6 illustrates contention-resolution diversity slotted aloha principle according to an embodiment of the disclosure.

[0035] Figure 7 illustrates an example of contention-resolution RACH-less transmission according to an embodiment of the disclosure.

[0036] Figure 8 illustrates network configured resources for a contention-resolution RACH-less frame according to an embodiment of the disclosure.

[0037] Figure 9 illustrates a UE selecting a number of slots based on a number of contention-resolution RACH-less transmission attempts according to an embodiment of the disclosure.

[0038] Figure 10 illustrates a contention-resolution RACH-less transmission procedure including multiple transmission instances according to an embodiment of the disclosure.

[0039] Figure 11 illustrates use of time alignment for contention-resolution RACH-less transmission according to an embodiment of the disclosure.

[0040] Figure 12 illustrates a timer being used to monitor for a network response for a contention-resolution RACH-less transmission according to an embodiment of the disclosure.

[0041] Figure 13 illustrates a RACH-less resource indication MAC control element according to an embodiment of the disclosure.

[0042] Figure 14 illustrates an example method for performing random access without Msg1 by a UE according to an embodiment of the disclosure.

[0043] Figure 15 is a block diagram of an exemplary network entity (e.g. UE or base station) that may be used in examples of the present disclosure according to an embodiment of the disclosure.

[0044] Hereinafter, embodiments of the disclosure will be described in detail with reference to the accompanying drawings.

[0045] In describing the embodiments, descriptions related to technical contents well-known in the art and not associated directly with the disclosure will be omitted. Such an omission of unnecessary descriptions is intended to prevent obscuring of the main idea of the disclosure and more clearly transfer the main idea.

[0046] 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.

[0047] The advantages and features of the disclosure and ways to achieve them will be apparent by making reference to embodiments as described below in detail in conjunction with the accompanying drawings. However, the disclosure is not limited to the embodiments set forth below, but may be implemented in various different forms. The following embodiments are provided only to completely disclose the disclosure and inform those skilled in the art of the scope of the disclosure, and the disclosure is defined only by the scope of the appended claims. Throughout the specification, the same or like reference numerals designate the same or like elements. Furthermore, in describing the disclosure, a detailed description of known functions or constitution incorporated herein will be omitted in the case that it is determined that the description may make the subject matter of the disclosure unnecessarily unclear. The terms which will be described below 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.

[0048] Herein, it will be understood that each block of the 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).

[0049] 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.

[0050] As used in embodiments of the disclosure, a "~unit" 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" does not always have a meaning limited to software or hardware. The "~unit" may be constructed either to be stored in an addressable storage medium or to execute one or more processors. Therefore, the "~unit" 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" may be either combined into a smaller number of components and a "~unit," or divided into additional components and a "~unit." Moreover, the components and "~units" 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" may include one or more processors.

[0051] It should be appreciated that the blocks in each flowchart and combinations of the flowcharts may be performed by one or more computer programs which include instructions. 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.

[0052] 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, a microprocessor unit (MPU), a system on chip (SoC), an IC, or the like.

[0053] 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.

[0054] 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.

[0055] 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.

[0056] 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.

[0057] 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.

[0058] 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.

[0059] 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.

[0060] 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.

[0061] 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.

[0062] 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.

[0063] 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.

[0064] 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, 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.

[0065] 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.

[0066] 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.

[0067] 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.

[0068] For example, the physical layer signalling may be referred to as Layer 1 (L1) signalling and may include downlink control information (DCI). In addition, the higher layer signalling may include a medium access control (MAC) control message, a radio resource control (RRC) signalling message, a non-access stratum (NAS) signalling message, or an application layer message. The RRC signalling message may be referred to as L3 (layer 3) signalling. It should be noted, however, that the higher layer signalling is not limited to the aforementioned examples.

[0069] 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.

[0070] 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.

[0071] 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.

[0072] In the specific embodiments of the present disclosure described below, 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.

[0073] The drawings or flowcharts described below illustrate exemplary 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.

[0074] 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.

[0075] 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.

[0076] 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 described below, 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) where appropriate.

[0077] Hereinafter, a base station 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 base station (BS), a wireless access unit, a BS controller, or a node on a network.

[0078] 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 5G base station architectures in which such CU and DU functional splits are implemented.

[0079] A terminal may include a UE, a mobile station (MS), a cellular phone, a smartphone, a computer, or a multimedia system capable of performing communication functions.

[0080] In the disclosure, a downlink (DL) refers to a radio link through which a BS transmits a signal to a UE, and an uplink (UL) refers to a radio link through which a UE transmits a signal to a BS.

[0081] Furthermore, hereinafter, 5th generation (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

[0082] 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."

[0083] Hereinafter, in the context of the present disclosure, higher layer signalling may refer to signalling 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, ...), radio resource control (RRC), or medium access control (MAC) control element (CE), or a non-access stratum (NAS) signalling message, or an application layer message. The RRC signalling message may be referred to as L3 (layer 3) signalling.

[0084] In addition, L1 signalling may refer to signalling corresponding to at least one or any combination of signalling techniques using the at least one or any combination of the following physical layer channels or signalling: physical downlink control channel (PDCCH), downlink control information (DCI), user equipment (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 signalling message may be referred to as a physical layer signalling.

[0085] 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 signalling or a higher layer signalling. Such an expression may be replaced with other terms having the same or substantially equivalent meaning.

[0086] Hereinafter, the operational principle of the present disclosure will be described in detail with reference to the accompanying drawings.

[0087] Figure 1 illustrates a non-terrestrial network architecture according to an embodiment of the disclosure.

[0088] In 3rdgeneration partnership project (3GPP) 5th generation (5G) new radio (NR), 3GPP 5G Release 18 has been frozen and work on Release 19 is currently underway. An aim of Release 19 is to develop and improve features.

[0089] Internet of things (IoT) non-terrestrial networks (NTNs) was a 3GPP study and work item in 3GPP release 17 to provide NTN access for evolved universal mobile telecommunications system terrestrial radio access network (E-UTRAN) IoT devices (narrowband (NB)-IoT and LTE-M / evolved machine type communication (eMTC)) [RP-202689, RAN#90 December 2020]. NR NTN was a work item in Rel-17 to specify adaptation to allow NR to function over NTN [RP-211557, RAN#91-e March 2021]. NTN access may be through lower earth orbit (LEO), medium earth orbit (MEO) and geostationary orbit (GEO), as well as through high-altitude platform systems (HAPS).

[0090] Following the Work items in Release 17 there were work items to enhance NR NTN [RP-220953, RAN#95-e March 2022] and IoT NTN [RP-223519, RAN#98-e December 2022] in Release 18.

[0091] The work item description for IoT NTN Rel-19 is the following [RP-234077]:

[0092] ●Support of Store&Forward (S&F) satellite operation with full E-UTRANNodeB(eNB) as regenerative payload, therefore:

[0093] ○Define the necessary enhancements into E-UTRAN(network & User Equipment (UE)) to support S&F operation for delay-tolerant services [RAN3,RAN2,RAN4]

[0094] ■At least specify necessary enhancements e.g. related to S1 protocol, especially to address the feeder link switch over as needed [RAN3].

[0095] Note: Strive tominimiseUEimpact.

[0096] Note: Coordination with SA2 (Rel-19 SA2 led Sat-Archph3SI) is needed on the detail requirements (e.g. traffic type, or Quality of Service (QoS) parameters for S&F), network architecture (e.g. whether consider (partial) core network on satellite) etc.; further coordination with CT1 might be required.

[0097] ●Support of Capacity enhancements foruplink(UL)

[0098] ○Study then specify, if beneficial, enhancements to enable multiplexing of multipleUEs(e.g. up to the min of 4 and the maximum allowed by the existing UL andDownlink(DL)signalling) in a single 3.75 kHz or15 kHzsubcarrier via orthogonal cover codes (OCC) forNPUSCHformat 1 andNPRACH[RAN1,RAN2].

[0099] ■Multi-tone support for15 kHzSCSshould also be considered

[0100] Note: Impact of impairment shall be taken into account.

[0101] ○Study and specify, if beneficial the following enhancements to reduce the necessaryuplinkanddownlinksignallingto complete an Early Data Transmission (EDT) transaction [RAN2]:

[0102] ■Msg3transmission withoutMsg1 / RAR

[0103] ■Efficient delivery (reduced overhead) ofmsg4 / Radio Resource Control(RRC)EarlyDataComplete

[0104] 5G New Radio

[0105] 5G NR is the latest cellular generation. 5G NR features several new innovations that allow for higher throughput, lower latency and extreme flexibility. Some of these important innovations are relevant to this disclosure.

[0106] - Beam-based procedures: The device will take into account the beams in a cell in several procedures to better accommodate the advancements in multi input multi output (MIMO) and beamforming seen over the last decade.

[0107] - Ultra-lean carriers: Reduction in the number of "always-on" signals where the network may broadcast reference signals a lot more infrequently compared to previous generations and allow a network to reduce the amount of system information broadcasted.

[0108] - More efficient state transitions: A new RRC state is introduced, RRC_INACTIVE. In RRC_INACTIVE, the UE performs similar actions as in RRC_IDLE, i.e. measuring and performing the cell reselection procedure to ensure that the UE is camping on the best cell. The network will save the UE context in the gNB and the UE will save the RRC configuration. This ensures that the state transition from RRC_INACTIVE and RRC_CONNECTED can be completed in a much smaller number of steps compared to moving from RRC_IDLE to RRC_CONNECTED. In a network where there are a lot of state transitions, this can reduce latency and improve capacity as there is a lot less need for control signals to occupy capacity and resources.

[0109] 5GNRProcedures

[0110] Below, some relevant 5G NR procedures are explained that are relevant to this disclosure.

[0111] Random Access and State Transitions

[0112] In 5G NR there are three different RRC states: RRC_IDLE, RRC_INACTIVE and RRC_CONNECTED.

[0113] To move to RRC_CONNECTED, a UE must first synchronize and connect to a cell, which it does through the random access procedure.

[0114] The 4-step random access procedure, which is the procedure introduced for the first release of 5G NR, the procedure would include a Msg1 and a Msg2. Msg1 consists of a preamble sent on the RACH, which signal a number from 1 to 64 identifying the UE. Msg2 is the random access response (RAR) which contains a timing advance to synchronize the UE, as well as an uplink grant to send Msg3. Msg3 contains an RRC message and Msg4 contains the reply to the first RRC message, as well as a contention resolution MAC CE to resolve any contention. For 2-step random access, the MsgA consists of both the preamble and the first RRC message. MsgB consists of the random access response to synchronize the UE, the reply to the first RRC message as well as contention resolution.

[0115] To move to RRC_CONNECTED from RRC_IDLE, the RRC Setup procedure is triggered. RRC Setup procedures establishes a signalling radio bearer 1 (SRB1) connection along with basic radio configurations. This means that the RRC message, RRCSetupRequest, will be included in Msg3 and the RRC message, RRCSetup, may be included in Msg4. After the RRC Setup procedures the network may also have to acquire capabilities, establish AS security before data can transmitted.

[0116] To move to RRC_CONNECTED from RRC_INACTIVE, the RRC Resume procedure is triggered. These procedures allow for the re-establishment of the full RRC connection, as well as resuming the AS security. This means that the RRC message, RRCResumeRequest, will be included in Msg3 and the RRC message, RRCResume, may be included in Msg4.

[0117] It should be noted that MAC random access procedures are often independent of the RRC procedures, which means that the random access procedures may in general be the same for RRC Setup, RRC Resume, RRC Re-establishment and RRC reconfiguration with sync.

[0118] RRC Release

[0119] One way to enter RRC idle or RRC inactive mode is by the network releasing the UE through the RRC release procedures. The RRC release procedures are initiated when the UE receives a RRCRelease message from the gNB.

[0120] The RRCRelease message sent from the gNB may in turn have been triggered by either the gNB or the AMF. This can for instance be due to any of the following reasons:

[0121] · Load balancing

[0122] · Re-direction (both in RRC idle and RRC inactive) to other frequencies or radio access technologies (RATs)

[0123] · UE context release triggered by the AMF (core network (CN))

[0124] · Suspend indication to send the UE to RRC inactive

[0125] · Failure to retrieve UE context when UE resumes RRC connection from RRC inactive

[0126] System information

[0127] System information is information that is broadcasted by a cell for a wide range of purposes. System information is divided into a set of system information blocks (SIBs). Some system information is required for a UE to access a cell. Without having acquired these system information blocks, the UE may not be allowed to access a cell. An example of such a SIB is SIB1 which contains access information, for instance a public land mobile network (PLMN) of the cell, the cell identity, the tracking area code as well as cell selection information. SIB1 also contains the serving cell radio configuration.

[0128] Another set of SIBs contain information on other frequencies and RATs for the purpose of idle and inactive mode cell reselection as well as related parameters. These are for instance in SIB2 to SIB5.

[0129] NarrowbandInternet of Things andLTE-M

[0130] Narrowband Internet of Things (NB-IoT) is a 3GPP-defined network based on 4G E-UTRAN that supports ultra-low complexity devices with very narrow bandwidth, that was introduced in 3GPP Release 13. It supports the massive machine type communication (mMTC) 5G use case for IMT-2020. The use case of NB-IoT is to serve massive IoT applications, where requirements for instance are to support enhanced coverage, power-efficient operation and a massive number of devices. Some of the features introduced are:

[0131] - Support for enhanced coverage through low bandwidth and extreme amounts of repetitions.

[0132] - Power efficient operation by allowing the UE to sleep for very long times, relaxed requirements and more efficient signal to establish with a cell.

[0133] LTE-M (or eMTC) is another technology that serves the mMTC 5G use case. Compared to NB-IoT, an LTE-M device is more like a simplified 4G E-UTRAN device with certain simplifications allowing for easier and cheaper implementation. It addresses a slightly wider use case compared to NB-IoT, with higher data rates and is not quite as power efficient as NB-IoT.

[0134] Both LTE-M and NB-IoT are specified with what is known as user plane (UP) and control plane (CP) enhancements for reduced signalling. In the UP solution, the UE supports AS security and Data radio bearers. In the CP, the UE does not support AS security and instead relies on NAS for security, which means that all data is routed through Mobility Management Entity (MME). CP is mandatory for NB-IoT and optional for LTE-M.

[0135] NTNSystem Information

[0136] As NTN has a number of NTN-specific information elements (IEs) that are only required when accessing an NTN cell and also due to the rather large information elements, it was agreed that new SIBs were needed.

[0137] In NR NTN, SIB19 contains the required information to access an NTN cell (38.331 V18.1.0 [1]).

[0138] As shown in Tables 1 and 2, SIB19 contains satellite assistance information for NTN access.

[0139]

[0140]

[0141] In IoT NTN, SIB31 contains the required information to access an IoT NTN cell (36.331 V18.1.0 [2]).

[0142] The IESystemInformationBlockType31contains satellite assistance information for the serving cell.SystemInformationBlockType31is only signalled for an NTN cell. An example related to theSystemInformationBlockType31is shown in Tables 3 and 4.

[0143]

[0144]

[0145] The system information contains the following:

[0146] - Serving cell Ephemeris elements - which allows UE to calculate the satellite position for doppler and time pre-compensation. This can be one of two formats:

[0147] o PVT format - which describes a (X,Y,Z) position as well as a speed vector (vX, vY, vZ)

[0148] o Orbital parameters - this describes the orbital movements of the satellite which is then used to infer the satellite position

[0149] - TA common parameters - this provides the common timing advance parameters which is introduced to compensate for the feeder link delays. The signalling consists of (in total taking up 57 bits)

[0150] o Absolute TA common, taking up 23 bits

[0151] o Drift of the TA common - how the TA common drifts, i.e. the first derivative, taking up 19 bits

[0152] o Variation of the TA common - how the TA common varies, i.e. the second derivative of the TA common, taking up 15 bits

[0153] - Synchronization validity duration - used to define how long the ephemeris and TA common is valid

[0154] - Epoch time - when the synchronization validity duration should start

[0155] - K-Offset - scheduling offset for timing relationship in NTN

[0156] - K-Mac - Scheduling offset used when the downlink and uplink frame timing is not aligned

[0157] - NR NTN specific information also includes (as part of 38.331):

[0158] o T-Service (signalled in SIB3 in IoT NTN)

[0159] o Reference location and distance threshold - used for location-based measurement initiation in RRC IDLE and RRC Connected mode

[0160] o Neighbour cell ephemeris

[0161] ■ This is used for idle mode measurements

[0162] NTNSystem Information Acquisition

[0163] Figure 2 illustrates an ephemeris synchronization process according to an embodiment of the disclosure.

[0164] As the ephemeris constantly changes due to the movement of the NTN payload, the UE needs to read the system information. There is furthermore a timer (T317 in IoT NTN and T430 in 5G NTN) associated with the ephemeris element that is started every time the system information containing the ephemeris (SIB31 in IoT NTN and SIB19 in NR NTN) is read. In IoT NTN, when T317 expires, the UE is no longer considered synchronized and it will have to re-acquire SIB31 in order to stay synchronized. In NR NTN, upon T430 expiry, the UE shall ensure that it has a recent ephemeris by reading the SIB in time by UE implementation. In IoT NTN, since an IoT UE (LTE-M and NB-IoT UE) is not expected to be able to acquire system information in connected mode, the UE tunes away and is likely unreachable while reading SIB31. If the IoT NTN UE is unable to read the SIB31 within a timer (T318) with a configured duration, the UE performs RLF similar to other cases where Radio Link Failure (RLF) is performed.

[0165] The T317 timer is different compared to a normal timer in RRC as it is not started at having received the SIB31. This is because the ephemeris has an epoch time, which is the reference point in time of when the ephemeris is defined. Thus the T317 is started from the epoch time, which may be in the past or in the future relative to have received SIB31. This means that in a UE implementation, the timer may be started with a different value with what was signalled according to what was signalled in the fieldul-SyncValidityDurationin SIB31.

[0166] Initial / Random Access Procedure inIoTNTN

[0167] Figure 3 illustrates an initial access procedure according to an embodiment of the disclosure.

[0168] As referred to the Figure 3, the steps related to the initial access procedure are normally as follows:

[0169] 0. UE determines the timing advance pre-compensation using the UE position and the satellite position. The UE position via Global Navigation Satellite System (GNSS), but other methods that do not rely on the network may also potentially be used, such as inertial navigation system or similar. The satellite position is acquired via SIB19 and the UE also pre-compensates using TA-Common, which is the common timing advance from the satellite to the ground gate way where the base station resides.

[0170] 1. UE uses the pre-compensation and sends Msg1 which is the RACH preamble. The RACH preamble will represent a number between 1 and 64. The number selected by the RACH is random, but there exists several rules to determine the range of preambles, depending on configurations and conditions - sometimes referred to as preamble division.

[0171] 2. If the network is able to detect and the determine the RACH preamble, the eNB responds with Msg2 or RAR.

[0172] 3. UE sends Msg3, which is sent using Physical Uplink Shared Channel (PUSCH). This message will contain the first RRC message. The RRC message depends on the specific reason why the random access procedure was triggered. For example, for initial access it will be RRCSetupRequest, for resuming it is RRCConnectionResumeRequest, for re-establishing RRC it is RRCConnectionReestablishmentRequest, for CP-EDT it is RRCEarlyDataRequest etc.

[0173] 4. Since it is possible that two UEs select the same Random Access Preamble ID (RAPID), there is a chance of collision. So in Msg4, sent over Physical Download Shared Channel (PDSCH), this contention may be resolved using the Contention Resolution MAC CE. Msg4 also contains an RRC message that is a response to Msg3. This can for instance be RRCConnectionSetup, RRCConnectionResume, RRCConnectionReestablishment, RRCReject, RRCEarlyDataComplete etc.

[0174] 5. Msg5 is a further message that is scheduled uplink message which would consist of the reply to the downlink RRC message in Msg4. Msg5 is sometimes not considered a part of the random access procedure, but a part of any access procedure. The RRC message carried in Msg5 may be RRCConnectionSetupComplete, RRCConnectionResumeComplete, RRCConnectionReestablishmentComplete and so on.

[0175] Early Data Transmission

[0176] Figure 4 illustrates an early data transmission procedure according to an embodiment of the disclosure.

[0177] EDT is a feature that allows a UE to start to transmit data already in Msg3. This is mostly for power-saving purposes where in the best case the UE would be able to transmit all of its data and then be released already in Msg4. In RRC Resume, the UE may not start transmitting data until after RRCResumeComplete in Msg5.

[0178] As referred to the Figure 4, the EDT procedure can be seen, from the perspective of PHY layer, MAC and RRC. The steps are follows:

[0179] 0. Same as in any random access procedure.

[0180] 1. Same as in any random access procedure, but the UE selects a RACH preamble from a specific set of preambles that indicates that the UE will perform EDT.

[0181] 2. If the network is able to detect and the determine the RACH preamble, the eNB responds with Msg1 or RAR.

[0182] 3. UE sends Msg3

[0183] 4. Since it is possible that two UEs select the same RAPID, there is a chance of collision. So in Msg4, sent over PDSCH, this contention may be resolved using the Contention Resolution MAC CE. Msg4 also contains an RRC message that is a response to Msg3. This can for instance be RRCSetup, RRCConnectionResume, RRCConnectionReestablishment, RRCReject, RRCEarlyDataComplete etc.

[0184] PreconfiguredUplinkResource

[0185] Figure 5 illustrates a preconfigured uplink resource procedure according to an embodiment of the disclosure.

[0186] PUR is a feature that allows for pre-configuring uplink transmissions without the need for random access. It also means that data can be transmitted without the UE needing to move to RRC connected, saving time and power consumption.

[0187] As referred to the Figure 5, the PUR procedure can be seen, from the perspective of PHY layer, MAC and RRC. The steps are follows:

[0188] 1. UE may optionally send a request to request the UE to be configured with PUR. This request contains the requested number of PUR occasions, the periodicity and offset as well as the Transport Block Size (TBS), i.e. the size of the allocation for PUR.

[0189] 2. If the network determines that the UE shall go to RRC idle and that it would be beneficial for the UE to be configured with PUR, then the network releases the UE and configures pur-Config in the RRCConnectionRelease message.

[0190] a. The PUR configuration contains the parameters that gives the PUR resource, such as periodicity and offset, the startSFN, the start subframe, the number of PUR occasions, the PUR-RNTI, the pur-TimeAlignmentTimer, and RSRP threshold, a response window timer, the configurations for MPDCCH, PDSCH, PUCCH and PUSCH and the PDSCH frequency hopping.

[0191] 3. The UE suspends the RRC connection and moves to RRC idle.

[0192] 4. Traffic arrives in the uplink buffer.

[0193] 5. In an NTN, the UE would at least have to self-precompensate the Timing advance. The UE may potentially also have to acquire the GNSS position as well as acquire SIB31 to ensure that it has the most updated satellite ephemeris.

[0194] 6. UE uses the configured PUR-resources and performs uplink transmission using PUSCH

[0195] a. In CP solution, the PUR message consists of the RRC message, RRCEarlyDataRequest, which contains the transparent NAS container which may contain data or NAS signalling.

[0196] b. In UP solution, the PUR message consists of the RRC message, RRCConnectionResumeRequest, as well as uplink data from any of the radio bearers that triggered the PUR.

[0197] 7. The UE responds to the PUR:

[0198] a. In CP solution, the response may consist of 1) a Layer 1 acknowledgement, 2) a Timing Advance MAC CE command that updates the TA or 3) an RRCEarlyDataComplete message. If none of these are received, the UE considers the procedure not to be completed.

[0199] b. In UP solution, the response consists of the RRCConnectionRelease message which successfully completes the PUR transmission. The response may also include downlink data transmissions.

[0200] In 3GPP Release 19 IoT NTN, the following objective can be seen:

[0201] ●Support of Capacity enhancements for UL

[0202] ○Study then specify, if beneficial, enhancements to enable multiplexing of multipleUEs(e.g. up to a minimum of 4 and a maximum allowed by the existing UL and DLsignalling) in a single 3.75 kHz or15 kHzsubcarriervia orthogonal cover codes (OCC) forNPUSCHformat 1 andNPRACH[RAN1,RAN2].

[0203] ■Multi-tone support for15 kHzSCSshould also be considered.

[0204] Note: Impact of impairment shall be taken into account.

[0205] ○Study and specify, if beneficial the following enhancements to reduce the necessaryuplinkanddownlinksignallingto complete an EDT transaction [RAN2]:

[0206] ■Msg3transmission withoutMsg1 / RAR

[0207] ■Efficient delivery (reduced overhead) ofmsg4 / RRCEarlyDataComplete.

[0208] This is with the following justification. Need for UL capacity enhancement: NB-IoT NTN is already being deployed live at this time. In these early and upcoming deployments, it is clearly emerging that IoT-NTN, in particular NB-IoT, will have to support massive capacity in terms of number and types of UE, some of which with worse characteristics than others (e.g. low cost devices, wearables, etc). Multiplexing of UEs by usage of OCC for NPUSCH format 1 and NPRACH should therefore be studied and if beneficial being specified.

[0209] Therefore, in order to unlock the additional UL capacity potential, there is a need to identify methods to de-couple the UL from the DL as much as possible.

[0210] Figure 6 illustrates contention-resolution diversity slotted aloha (CRDSA) principle according to an embodiment of the disclosure.

[0211] The CRDSA is a technique for performing random access. The CRDSA technique allows contention in random access to be resolved via successive interference cancellation (SIC). It relies on successfully decoding a packet and using that successful decoding to remove the contribution of the packet from a collision in order to successfully decode a collision. This is done by replicating packets and sending them in multiple slots. The principle of CRDSA can be illustrated in Figure 6, where the colored rectangles are packet transmissions for a specific user.

[0212] As illustrated in the Figure 6, slot 2, 3 and 5 have collisions. Without any special techniques it would only be possible to detect slot 1 and slot 4, i.e. user 2 and user 3. Using CRDSA, the receiver, i.e. the network, first detects slots where there are transmissions without collisions. Under good radio conditions, the receiver successfully decodes User 2 in slot 1 and User 3 in slot 4. The network will also have received signalling on which other slots that User 2 and User 3 will have replicated its transmission, which is in slot 2 and slot 3 respectively. Using this, the receiver removes the contribution from User 2 in slot 2, . Once again under ideal conditions the UE is able to decode User 1. The next step is that UE removes the contribution from User 3 in slot 3, . In this way, the receiver has successfully decoded all of the packets.

[0213] Using these methods, the random access procedure can be made a lot more efficient for cases where only a small amount of data is to be delivered.

[0214]

[0215] The following examples are applicable to, and use terminology associated with, 3GPP 5G. However, the skilled person will appreciate that the techniques disclosed herein are not limited to these examples or to 3GPP 5G, and may be applied in any suitable system or standard, for example one or more existing and / or future generation wireless communication systems or standards. The skilled person will appreciate that the techniques disclosed herein may be applied in any existing or future releases of 3GPP 5G NR or any other relevant standard.

[0216] For example, the functionality of the various network entities and other features disclosed herein may be applied to corresponding or equivalent entities or features in other communication systems or standards. Corresponding or equivalent entities or features may be regarded as entities or features that perform the same or similar role, function, operation or purpose within the network. For example, the functionality of an IAB node in the examples below may be applied to any other suitable type of entity performing functions of a network node.

[0217] The skilled person will appreciate that the present invention is not limited to the specific examples disclosed herein. For example:

[0218] ● The techniques disclosed herein are not limited to 3GPP 5G.

[0219] ● One or more entities in the examples disclosed herein may be replaced with one or more alternative entities performing equivalent or corresponding functions, processes or operations.

[0220] ● One or more of the messages in the examples disclosed herein may be replaced with one or more alternative messages, signals or other type of information carriers that communicate equivalent or corresponding information.

[0221] ● One or more further elements, entities and / or messages may be added to the examples disclosed herein.

[0222] ● One or more non-essential elements, entities and / or messages may be omitted in certain examples.

[0223] ● The functions, processes or operations of a particular entity in one example may be divided between two or more separate entities in an alternative example.

[0224] ● The functions, processes or operations of two or more separate entities in one example may be performed by a single entity in an alternative example.

[0225] ● Information carried by a particular message in one example may be carried by two or more separate messages in an alternative example.

[0226] ● Information carried by two or more separate messages in one example may be carried by a single message in an alternative example.

[0227] ● The order in which operations are performed may be modified, if possible, in alternative examples.

[0228] ● The transmission of information between network entities is not limited to the specific form, type and / or order of messages described in relation to the examples disclosed herein.

[0229] To satisfy extremely high data rate requirements, the 3GPP 5G NR standard utilises communication frequencies in a relatively high range, from 30 GHz to 300 GHz, corresponding to wavelengths in the millimetre (mm) range (mmWave communication). Such mmWave communication provides a large available bandwidth and high transmission speeds. However, problems with mmWave communication include severe signal path loss and low penetration, resulting in a relatively short transmission range. This in turn requires a greater density of base stations deployment.

[0230] Certain examples of the present disclosure provide a network or wireless communication system comprising a first network entity and a second network entity according to any example, embodiment, aspect and / or claim disclosed herein.

[0231] Certain examples of the present disclosure provide a computer program comprising instructions which, when the program is executed by a computer or processor, cause the computer or processor to carry out a method according to any example, embodiment, aspect and / or claim disclosed herein.

[0232] Certain examples of the present disclosure provide a computer or processor-readable data carrier having stored thereon a computer program according to the preceding examples.

[0233] Certain examples of the present disclosure may be provided in the form of an apparatus / device / network entity configured to perform one or more defined network functions and / or a method therefor. Such an apparatus / device / network entity may comprise one or more elements, for example one or more of receivers, transmitters, transceivers, processors, controllers, modules, units, and the like, each element configured to perform one or more corresponding processes, operations and / or method steps for implementing the techniques described herein. For example, an operation / function of X may be performed by a module configured to perform X (or an X-module). Certain examples of the present disclosure may be provided in the form of a system (e.g. a network) comprising one or more such apparatuses / devices / network entities, and / or a method therefor. For example, in the following examples, a network may include one or more IAB nodes.

[0234] It will be appreciated that examples of the present disclosure may be realized in the form of hardware, software or a combination of hardware and software. Certain examples of the present disclosure may provide a computer program comprising instructions or code which, when executed, implement a method, system and / or apparatus in accordance with any aspect, claim, example and / or embodiment disclosed herein. Certain embodiments of the present disclosure provide a machine-readable storage storing such a program.

[0235] The same or similar components may be designated by the same or similar reference numerals, although they may be illustrated in different drawings.

[0236] Detailed descriptions of techniques, structures, constructions, functions or processes known in the art may be omitted for clarity and conciseness, and to avoid obscuring the subject matter of the present disclosure.

[0237] Certain examples of the present disclosure disclose protocol-aspects for RACH-less transmissions where the receiver employs success interference cancellation (SIC) algorithms to decode packets that are sent by UEs.

[0238] All examples in this disclosure may apply to any of NR NTN, LTE-M / eMTC NTN, E-UTRAN NTN, 6G NTN.

[0239] In this disclosure, the term "RACH-less transmission" is used to 1) indicate a procedure where user plane data and control plane signalling can be transmitted in a contention-based manner without having to perform random access, 2) any procedure where random access is performed, but Msg1 and Msg2 is skipped.

[0240] This may also be called, or the methods of the disclosure may also apply to, contention-based PUR, or EDT without Msg1 or similar. RACH-less transmission may also be termed "Msg3 without random access". This can be a generalization of RACH-less transmission where any procedure which normally uses a random access procedure, may perform the random access procedure but only transmit Msg3.

[0241] In this disclosure, the term "contention-resolution RACH-less transmission" is used, which may be taken to mean transmitting a message where successive interference cancellation techniques are designed to be used. However, some of the aspects of this invention may not necessarily apply only to random access procedures where successive interference cancellation is applied, but may also apply to general contention-based RACH-less transmission performance.

[0242] These procedures may or may not require a UE to have synchronized by acquiring its own location, for instance via GNSS, and acquiring NTN assistance information (potentially comprising of ephemeris of the NTN network node, i.e. satellite).

[0243] The disclosure may also apply to small data transmission (SDT), which is a 5G NR feature where a UE sends data while in a RRC_INACTIVE state. It may for instance apply to random access SDT (RA-SDT), where the random access procedure (Msg1 / Msg2) is replaced by sending a Msg3 in a contention-based manner as described in this disclosure.

[0244] Figure 7 illustrates an example of contention-resolution RACH-less transmission according to an embodiment of the disclosure.

[0245] As referred to the Figure 7, the example of a contention-resolution RACH-less transmission can be seen, and the steps are as follows:

[0246] 0a. UE is configured in a dedicated or broadcasted manner with contention-resolution RACH-less transmission.

[0247] 0b. UE may be in a RRC_IDLE state or a RRC_INACTIVE state, i.e. in a RRC non-connected state without resources. However the UE being in an RRC connected state is not be precluded in this disclosure.

[0248] 1. UE selects contention-resolution RACH-less resources.

[0249] 2. UE sends a contention-resolution RACH-less transmission. The transmission may consist of any type of RRC message for a specified purpose. For instance, for EDT, the transmission may consist of a RRCEarlyDataRequest message (which may contain UL data) or a RRCResumeRequest message along with user plane data from a DRB. The transmission may also consist of a RRCSetup message or any other RRC message to either identify the UE, deliver data or setup an RRC connection with a cell or a base station. The transmission may also contain any relevant MAC Control Elements (CEs).

[0250] 3. eNB receives a contention-resolution RACH-less transmission from a set of UEs and applies a successive interference cancellation algorithm to resolve collisions.

[0251] 4. UE receives a response message to the contention-resolution RACH-less transmission. The response message may comprise a response message to the contention-resolution RACH-less transmission sent by the UE. The response message may be an RRC message in response to the contention-resolution RACH-less transmission sent by the UE. In EDT, the response message may be any of a RRCEarlyDataComplete message (which may contain DL data), a RRCResume message, a RRCRelease message, a RRCSetup message, along with user plane data from a DRB. The response message may be any setup message to establish an RRC connection containing RRC configurations, or any type of reject, release or suspend message.

[0252] 5. A number of steps may occur here. If an attempt to send a contention-resolution RACH-less transmission is not successful, a) UE may be configured to re-attempt the contention-resolution RACH-less transmission or b) UE may be configured to fallback to legacy random access. If the attempt was successful or failed, c) UE may be configured to move to a RRC_CONNECTED state or d) to move to a RRC_IDLE state or a RRC_INACTIVE state or any other non-connected RRC state.

[0253] Concepts from 4G and 5G and potential equivalents in a 6G system:

[0254] - 4G and 5G RRC connected state - UE having established a connection with a RAN, i.e. a cell, gNB or similar entity.

[0255] - Cell - This may be a different concept in a 6G system. For instance in a cell-less case a UE may attach, connect and be associated with a beam or other similar entity.

[0256] - RRC idle state - UE not in a RRC connected state, i.e. not having established a connection. RRC idle state also means that the UE will be camping on a cell or similar entity and then performing measurements and evaluating these to find a better cell or similar entity.

[0257] - 5G RRC inactive state - UE in a state similar to RRC idle state where the UE stores RRC configuration and resumes a RRC connection using the configuration. The network also stores the UE context and uses it to restore the UE connection.

[0258] - 5G RRC procedures (RRC Setup, RRC Resume, RRC Re-establishment, RRC Reconfiguration) - Any procedure that aims to establish a connection with a cell, a gNB or similar entity. For instance a procedure that aims to establish a 5G-6G Dual Connectivity setting with a 5G and 6G cell.

[0259] - Random access - The process of synchronizing the MAC layer via sending a preamble and receiving a message that synchronizes the uplink, as well as following messages to resolve any contention.

[0260] - Radio link failure (RLF) - Failure of the radio link, which may be a failure based on measured radio signals, or based on operation in the cell, such as a number of retransmissions, random access failures, the radio beams failing, etc. After the radio link failure, the UE may try to reselect to another cell and re-establish the RRC connection.

[0261] - Handover - Performing active mobility to another cell, gNB or similar entity.

[0262] - Releasing RRC connection - The UE is released via a message, such as a RRC Release message, that releases the RRC connection which the UE has to one or more cells.

[0263] In some examples, contention-resolution RACH-less transmission may be available for any UE to use. In some examples, contention-resolution RACH-less transmission may be configurable in a UE. Contention-resolution RACH-less transmission may be configurable via, for example, RRC connection release. Contention-resolution RACH-less transmission may, for example, be configurable when a UE is released to a RRC inactive state. Contention-resolution RACH-less transmission may, for example, be configurable when a RRC connection for a UE is suspended and the UE is in a RRC_IDLE state. For example, the UE may be configured in a suspend configuration or when the suspend indication is sent in the RRC release message.

[0264] While Figures 6, 9 and 10 of the disclosure indicate that the UE transmissions are aligned, in reality due to somewhat unsynchronized UEs, the timing of the transmissions may be off and not fully aligned.

[0265] Selecting of Resources

[0266] Figure 8 illustrates network configured resources for a contention-resolution RACH-less frame according to an embodiment of the disclosure.

[0267] Network configured resources for contention-resolution RACH-less transmission may consist of a number of slots of a contention-resolution RACH-less transmission frame in which UEs can transmit. The slots may be time slots. The time slots are denoted M, as seen in 8A of Figure 8. The slots may be frequency slots. Contention-resolution RACH-less transmissions may be frequency division multiplexed The frequency slots are denoted M, as seen in 8B of Figure 8. Each slot may consist of multiple physical resource blocks (PRBs), which may be configurable.

[0268] A UE may create a transmission message and send the message using multiple contention-resolution RACH-less transmission instances, in multiple slots of a contention-resolution RACH-less transmission frame. The UE may send the same message in each contention-resolution RACH-less transmission instance. A UE may select specific slots in a contention-resolution RACH-less transmission frame in which to transmit the contention-resolution RACH-less transmission instances.

[0269] The contention-resolution RACH-less transmission instances may comprise a first contention-resolution RACH-less transmission instance and one or more further contention-resolution RACH-less transmission instances. The first and one or more further contention-resolution RACH-less transmission instances are sent by a UE at the same time.

[0270] A UE may determine a number of further contention-resolution RACH-less transmission instances to be used. A number of further contention-resolution RACH-less transmission instances to be used by a UE may be determined for the UE. A number of further contention-resolution RACH-less transmission instances to be used by a UE may be configurable by a network of the UE. A number of further contention-resolution RACH-less transmission instances to be used by a UE may be configurable in a broadcasted configuration by a network of the UE. A number of further contention-resolution RACH-less transmission instances may be a fixed number for each UE of a network.

[0271] A number of further contention-resolution RACH-less transmission instances to be used by a UE will determine a number of slots of a contention-resolution RACH-less transmission frame in which to transmit. In this disclosure, the number of slots can be denoted N. For example, a UE may use a first contention-resolution RACH-less transmission instance and one further contention-resolution RACH-less transmission instance requiring transmission in 2 slots out of, for example, a total of 6 contention-resolution RACH-less transmission slots of a contention-resolution RACH-less transmission frame.

[0272] In another aspect of the disclosure, a number of further contention-resolution RACH-less transmission instances used by a UE may be different for different UEs. For example, a UE may be configured in a dedicated manner with a number of further contention-resolution RACH-less transmission instances to be used by the UE that differs from other UEs. The other UEs may be configured with a number of further contention-resolution RACH-less transmission instances in a broadcasted manner.

[0273] In another aspect of the disclosure, a number of further contention-resolution RACH-less transmission instances to be used by a UE may be selected randomly. The number of further contention-resolution RACH-less transmission instances may be selected randomly from a range of values, where the range of values may be configurable.

[0274] In another aspect of the disclosure, a UE may select a number of further contention-resolution RACH-less transmission instances based on coverage of the UE by a cell. The UE may select a larger number of further contention-resolution RACH-less transmission instances if cell coverage is worse and a smaller number of further contention-resolution RACH-less transmission instances if cell coverage is better. The cell coverage may, for example, be represented by signal strength, such as RSRP, or by signal quality, such as SINR. A UE may select a number of further contention-resolution RACH-less transmission instances using one or more thresholds. For example, a UE may select a number of further contention-resolution RACH-less transmission instances depending on cell signal strength or cell signal quality being any of between one or more thresholds, above one or more thresholds, below one or more thresholds.

[0275] In another aspect of the disclosure, a UE may select a number of further contention-resolution RACH-less transmission instances based on a number of failed contention-resolution RACH-less transmission attempts.

[0276] Figure 9 illustrates a UE selecting a number of slots based on a number of contention-resolution RACH-less transmission attempts according to an embodiment of the disclosure.

[0277] A UE may increase a selected number of further contention-resolution RACH-less transmission instances if one or more UE contention-resolution RACH-less transmission attempts fail. For example, a UE may be configured to attempt to transmit one further contention-resolution RACH-less transmission instance. If this attempt fails, the UE may be configured to attempt to transmit two further contention-resolution RACH-less transmission instances. If this attempt fails, the UE may be configured to attempt to transmit three further contention-resolution RACH-less transmission instances. A UE may be configurable to select one further contention-resolution RACH-less transmission instance in a first contention-resolution RACH-less transmission attempt and select two further contention-resolution RACH-less transmission instances in a following contention-resolution RACH-less transmission attempt. This may achieve a balance when there is a low load on the network, as when there is a low load on the network, there is likely no need to transmit two further contention-resolution RACH-less transmission instances. Two further contention-resolution RACH-less transmission instances is a minimum number in order for a receiver to be able to perform successive interference cancellation. This method of selecting a number of further contention-resolution RACH-less transmission instances may be different from, for example, selecting an increased number of further contention-resolution RACH-less transmission instances based on coverage of a cell. This is because, in this case, the likelihood of a transmission packet being successfully decoded increases substantially with a larger number of further contention-resolution RACH-less transmission instances if there is a lot of load on the network. This increasing of further contention-resolution RACH-less transmission instances may only be configured to UEs with higher priority, or may be dedicatedly configured. A UE may be configured to be allowed to use increasing of further contention-resolution RACH-less transmission instances once. Increasing of further contention-resolution RACH-less transmission instances may be allowed for one or more types of traffic. For example, increasing of further contention-resolution RACH-less transmission instances may be allowed for any of control plane traffic, emergency signalling traffic.

[0278] Contention-resolution RACH-less transmission using a single further contention-resolution RACH-less transmission instance and contention-resolution RACH-less transmission using multiple further contention-resolution RACH-less transmission instances may be allowed. If, for a UE, contention-resolution RACH-less transmission with a single further contention-resolution RACH-less transmission instance fails, the UE may use contention-resolution RACH-less transmission with multiple further contention-resolution RACH-less transmission instances. In the latter, a receiver may use successive interference cancellation.

[0279] A UE may be configured with any of a minimum number of multiple further contention-resolution RACH-less transmission instances, a maximum number of multiple further contention-resolution RACH-less transmission instances.

[0280] A UE may select one or more specific slots within a contention-resolution RACH-less transmission frame in which to transmit a first and one or more further contention-resolution RACH-less transmission instances. A UE may randomly select the one or more specific slots within a contention-resolution RACH-less transmission frame in which to transmit the first and one or more further contention-resolution RACH-less transmission instances. In one aspect of the disclosure, a UE may randomly select one or more slots within a contention-resolution RACH-less transmission frame in which to transmit based on a number of further contention-resolution RACH-less transmission instances.

[0281] In another aspect of the disclosure, a UE may randomly select a number of slots within a contention-resolution RACH-less transmission frame in which to transmit a first and one or more further contention-resolution RACH-less transmission instances. For example, a UE may generate a random number which represents a number of slots within a contention-resolution RACH-less transmission frame in which to transmit a first and one or more further contention-resolution RACH-less transmission instances. The UE may generate the random number by selecting a number between 0 and 2^M-1, where M is a contention-resolution RACH-less transmission / CRDSA frame size. The number of slots may be derived by transforming the random number to a bit string of size M. For example, if M=8, the random number is 48 = 0*2^0 + 0*2^1 +0*2^2 + 0*2^3 + 1*2^4 + 1*2^5 + 0*2^6 + 0*2^7, resulting in the string 00001100. 00001100 which means that the UE transmits two further contention-resolution RACH-less transmission instances (N=2) in slots 5 and 6 (it could potentially also mean slots 3 and 4).

[0282] A UE may also select slots in which to transmit within a contention-resolution RACH-less transmission frame of other frequencies or carriers. The UE may select the slots and the other frequencies jointly. The UE may select a frequency or a carrier first.

[0283] Configurable Parameters

[0284] Network configurable parameters for contention-resolution RACH-less transmission may include:

[0285] - Start slot of the contention-resolution RACH-less transmission frame

[0286] - Number of slots that make up the contention-resolution RACH-less transmission frame

[0287] - Number of PRBs for each slot

[0288] - Frequency start - i.e. where in frequency the contention-resolution RACH-less transmission resources are located

[0289] - Number of frequency layers

[0290] - The carrier, carrier component or bandwidth part in which contention-resolution RACH-less transmission instances are configured

[0291] ○ The configuration may be part of a specific bandwidth part that is only used for contention-resolution RACH-less transmission

[0292] - Number of further contention-resolution RACH-less transmission instances.

[0293] Contention-ResolutionRACH-less Transmission

[0294] A UE may indicate to, for example, an eNB or cell, one or more slots in which it has transmitted one or more further contention-resolution RACH-less transmission instances. This is used once the eNB has successfully decoded a further contention-resolution RACH-less transmission instance in a slot, which is then used for successive interference cancellations (SICs) in other slots where interference is occurring and preventing decoding of another further contention-resolution RACH-less transmission instance.

[0295] In one aspect of the disclosure, a UE may indicate a number of further contention-resolution RACH-less transmission instances in a bit string, where 0 means that a UE will not transmit on a specific slot and 1 indicates that the UE will transmit a further contention-resolution RACH-less transmission instance on a specific slot. For example, if M=8 and N=3, and the UE transmits in slot 0, 3 and 6, the indication of the number of further contention-resolution RACH-less transmission is 10010010.

[0296] A UE may indicate any number, field or identity that indicates slots in which further contention-resolution RACH-less transmission instances are transmitted. A UE may indicate any number, field or identity that indicates a number of slots. This may also be considered to be a resource identity.

[0297] A UE may indicate one or more slots in which further contention-resolution RACH-less transmission instances are transmitted by indicating a number that represents a number of options of slots in which to transmit further contention-resolution RACH-less transmission instances. For example, if M=5 and N=2, the number of options would be 11000, 10100, 10010, 10001, 01100, 01010, 01001, 00110, 000101, 00011. This is a total of ten options. The UE may choose one or more options and signal the chosen number of options. This can reduce a number of bits required to represent the slots in which the further contention-resolution RACH-less transmission instances were transmitted.

[0298] If a UE transmits further contention-resolution RACH-less transmission instances on different frequencies, the UE may include the frequencies in an indication of slots in which the further contention-resolution RACH-less transmission instance are transmitted.

[0299]

[0300] A UE may include a randomly-selected UE ID in the contention-resolution RACH-less transmission. A UE may be configurable to include a randomly-selected UE ID. The randomly-selected UE ID may, for example, be a number of bits that identify the UE. The randomly-selected UE ID may be used, for example, if two UEs select the same resource. The randomly-selected UE ID may be a small number of bits. This reduces the chance of two UEs selecting the same resource and there not being any way of distinguishing them.

[0301] The randomly-selected UE ID may be included in a MAC CE that is included in the or each further contention-resolution RACH-less transmission instance. One example can be found in Example #1. When a UE performs contention-resolution RACH-less transmission, a MAC CE may be configured to include a randomly-selected UE ID. The MAC CE may or may not have an LCID number associated with it.

[0302] When a UE transmits a single further contention-resolution RACH-less transmission instance, the UE may be configured not to include an indication of resources used for the transmission. When a UE transmits two or more further contention-resolution RACH-less transmission instances, the UE may be configured to include an indication of resources used for the transmission instances.

[0303] The indication of resources used for a contention-resolution RACH-less transmission may be included in any of a physical layer control message, such as a PUCCH, a higher layer message, such as an RRC message.

[0304] When an indication of resources used for a contention-resolution RACH-less transmission is included in a PUCCH, a UE may transmit the indication of resources used for the contention-resolution RACH-less transmission in a resource that is not used for successive interference cancellation. The PUCCH resources are therefore designed to not collide, or be less likely to collide, or be semi-orthogonal resources. This can be achieved by the PUCCH using different frequency, time or code resources.

[0305] A further contention-resolution RACH-less transmission instance may consist of a redundancy version (RV). A redundancy version may be a part of a punctured code word that is output by a decoder. In LTE there are four different redundancy versions, which are punctured from a larger code word.

[0306] In one aspect of the disclosure, the or each further contention-resolution RACH-less transmission instance may use a different RNTI. The RNTI may be dependent on slot. Different frequencies may also use different RNTIs.

[0307] Contention-resolution RACH-less transmission procedure, or CRDSA, may also include repetitions of one or more further contention-resolution RACH-less transmission instances. In this case, resources in which a UE transmits a further contention-resolution RACH-less transmission instance may not be a single slot, but rather multiple slots. This may be done in two ways as seen in Figure 10.

[0308] Figure 10 illustrates a contention-resolution RACH-less transmission procedure including multiple transmission instances according to an embodiment of the disclosure.

[0309] In (a), the repetitions are started in every R=2 slots, while in (b), the repetitions can start in any slot.

[0310] There may be one or more conditions for performing contention-resolution RACH-less transmission. If a UE does not fulfil the one or more conditions, the UE may, for example, be configured to perform a legacy random access procedure with RACH.

[0311] When transmitting a contention-resolution RACH-less transmission, a UE received power level may be approximately equal for all UEs. This means that if a UE determines that it is not capable of maintaining a certain received power level at a network receiver, the UE will not transmit contention-resolution RACH-less transmissions. Thus in one aspect of the disclosure, a condition for a UE to perform one or more contention-resolution RACH-less transmissions may be that the UE can achieve a specified received power level at a receiver. The specified received power level may be configurable by the network.

[0312] In one aspect of the disclosure, a condition for a UE to perform one or more contention-resolution RACH-less transmissions may be that the UE has not performed a previous contention-resolution RACH-less transmission in a specified time. This can be useful to ensure that resource load is kept manageable.

[0313] Other conditions for a UE to perform one or more contention-resolution RACH-less transmissions may be:

[0314] - a UE has a signal strength (RSRP) or signal quality (RSRQ / SINR) greater than or equal to a specified threshold. The specified threshold may be configurable.

[0315] - a UE data buffer fulfils a specified condition. The data buffer specified condition may be that a size of the data buffer is larger or smaller than a specified threshold. The specified threshold may be configurable.

[0316] - a UE is sufficiently synchronized, i.e. has acquired GNSS position and / or a satellite ephemeris recently.

[0317] If the above conditions are not fulfilled, a UE may be configured to perform legacy random access, i.e. random access with a RACH preamble.

[0318] One of the more difficult aspects of UE contention-resolution RACH-less transmission is that there is a need to ensure that UEs are reasonably well-synchronized in order for successive interference cancellation to work well.

[0319] One condition for a UE to perform one or more contention-resolution RACH-less transmissions may be that the UE has a valid timing advance. The UE may establish the timing advance by sending a RACH preamble in a Msg1 and receiving a Msg2 RAR. The timing advance may then be used in future contention-resolution RACH-less transmission instances.

[0320] In another aspect of the disclosure, a timing advance received at any time, for example when a UE is in a RRC connected state, may be considered valid when a satellite ephemeris or the UE position is considered valid. As a more specific example, a timing advance may be considered valid if NTN assistance information (for example consisting of satellite ephemeris) is valid within a period in which the timing advance is received by a UE. A UE may first receive NTN assistance information, where the NTN assistance information will be valid for a specified time. A last received timing advance will be valid and the UE will be considered to be timing-aligned, as long as the NTN assistance information is valid. When the NTN assistance information is no longer valid (for example timer T317 or T430 has expired), the UE will no longer be considered to be timing-aligned for performing one or more contention-resolution RACH-less transmissions, or the UE is not considered synchronized for performing one or more contention-resolution RACH-less transmissions. This also means that the timing alignment is considered expired once the NTN assistance information validity has expired. In another aspect of the disclosure, a UE is no longer considered to be timing-aligned for one or more contention-resolution RACH-less transmissions based on a previously-received timing advance if a new GNSS measurement has been performed, or if a GNSS position validity has expired or if a GNSS position has gone out of date. The timing alignment is considered valid until the GNSS position is out-of-date. An example of this can be seen in Figure 11.

[0321] Figure 11 illustrates use of time alignment for contention-resolution RACH-less transmission according to an embodiment of the disclosure.

[0322] This may for instance mean that the timing-alignment (potentially for contention-resolution RACH-less transmission) is not reset or cancelled when a UE moves from a RRC connected state to a RRC idle state.

[0323] The network may configure UE timing alignment for the purpose of contention-resolution RACH-less transmission. The network may configure the UE timing alignment in an RRC connection release message. The network may configure a UE to maintain timing alignment for performing contention-resolution RACH-less transmission after the UE leaves a RRC connected state. The network may indicate to the UE in a RRC release message that the UE shall maintain the timing alignment with a cell or with a satellite.

[0324] In one aspect of the disclosure, a UE may perform contention-resolution RACH-less transmission with either a cell that released the UE, or a satellite that released the UE. Knowing that it is the same satellite can be deduced from the satelliteID that is indicated in SIB31 or SIB33.

[0325] As an example, for a CP-IoT case, contention-resolution RACH-less transmission may consist of the following messages on the MAC layer : 1) a MAC CE indicating the position of the replicas and 2) an RRC message. The RRC message may be an EarlyDataRequest message.

[0326] As an example, for a UP-IoT or SDT case, contention-resolution RACH-less transmission may consist of the following messages on the MAC layer: 1) a MAC CE indicating a position of the replicas, 2) an RRC message and 3) UL data from a DRB. The RRC message may be an RRCResumeRequest message or any other similar RRC message.

[0327] Response

[0328] In a network response message, in one aspect of the disclosure, a network includes an indication that identifies a UE that transmitted using contention-resolution RACH-less transmission resources.

[0329] The indication identifying the UE may, for example, be based on identifying where the UE transmitted. The indication may, for example, indicate slots where all of the further contention-resolution RACH-less transmission instances were transmitted. The indication may be based on an indication that the UE sent to the network comprising where the UEs sent the further contention-resolution RACH-less transmission instances. The indication may be used if a first contention-resolution RACH-less transmission instance from the UE to the network was successfully decoded by the network.

[0330] The indication identifying the UE may indicate a slot used in a contention-resolution RACH-less transmission instance. The indicated slot may be used if the network failed to correctly decode the contention-resolution RACH-less transmission instance. If a UE receives an indication of only a single slot where it transmitted, and no other indication that matches which slots that it transmitted in, then the UE may know that its contention-resolution RACH-less transmission failed. For instance, if a UE transmits further contention-resolution RACH-less transmission instances in two slots, and the UE receives a response indicating only one of these slots, the UE may assume a transmission failure.

[0331] The indication identifying the UE may indicate a part of a correctly-decoded message. The part may be, for example, 20 bits of a successfully decoded (but potentially encrypted) message.

[0332] The indication identifying the UE may contain an indication of where in frequency the UE transmitted the contention resolution RACH-less transmission. The indication may be direct or implicit.

[0333] In one aspect of the disclosure, a network response received by a UE may indicate success or failure of a contention-resolution RACH-less transmission instance of the UE. Success of a contention resolution RACH-less transmission instance may be indicated to the UE by a network response including, for example, any of a UE ID that matches the UE, a number that indicates in which slots further contention-resolution RACH-less transmission instances were transmitted by the UE, an RRC payload in response to a first contention-resolution RACH-less transmission of the UE.

[0334] Failure of a contention-resolution RACH-less transmission instance may be indicated to the UE by a lack of an indication of success. For example, if only one slot in which the UE transmitted is indicated to the UE, when the UE transmitted multiple further contention-resolution RACH-less transmission instances, the UE may consider the transmission as having failed.

[0335] In one aspect of the disclosure, a network response to a UE may contain:

[0336] - A timing advance command. The command may be present in a network response message from the network to the UE. The command may be present in any of a message signalling success of a contention-resolution RACH-less transmission, a message signalling failure of a contention-resolution RACH-less transmission. The command may be used for success of a contention-resolution RACH-less transmission if the network is to continue communication with the UE or request the UE to enter a RRC_CONNECTED state. The command may be used for failure of a contention-resolution RACH-less transmission if the network can detect a timing advance.

[0337] - A backoff indication. The backoff indication may be indicated by the network for failure of a contention-resolution RACH-less transmission and when a UE should back off from further transmissions. This will ease resource load.

[0338] - A fallback indication. The fallback indication may be indicated by the network for failure of a contention-resolution RACH-less transmission to indicate to a UE to stop attempting transmissions on contention-resolution RACH-less resources.

[0339] A network response for contention-resolution RACH-less transmission may require monitoring for the response. One important part is to determine a RNTI to use to monitor for the response.

[0340] In one aspect of the disclosure, a RNTI may be calculated based on a contention-resolution RACH-less transmission frame on which a UE performs transmission. This can be done by numbering the frames and then using these to calculate the RNTI.

[0341] In another aspect of the disclosure, a RNTI for monitoring for a network response may be based on one or more slots that in which a UE transmits one or more further contention-resolution RACH-less transmission instances. As an example, the UE may calculate the RNTI based on the first slot or last slot that the UE transmits the RNTI in. For example, if the UE transmits in slot 2 and slot 5 of a contention-resolution RACH-less transmission frame, the slot 2 will be used to compute the RNTI to be used to monitor for the network response.

[0342] The frequency of a contention-resolution RACH-less transmission frame or a slot may also be used to calculate a RNTI.

[0343] A timer may be used to monitor for a network response for contention-resolution RACH-less transmission. The timer may be configured to start at a specified time after an end of the contention-resolution RACH-less transmission frame. This is different from a normal case of starting to monitor for a network response after a random access-like transmission, which normally starts just after the physical transmission. This can be seen in Figure 12.

[0344] Figure 12 illustrates a timer being used to monitor for a network response for a contention-resolution RACH-less transmission according to an embodiment of the disclosure.

[0345] The timer may be configured to start a specified time after an end of a first or last slot where a contention-resolution RACH-less transmission instance was transmitted.

[0346] Re-attempting and Fallback

[0347] If a contention-resolution RACH-less transmission attempt fails, a UE may re-attempt a contention-resolution RACH-less transmission.

[0348] In one aspect of the disclosure, a contention-resolution RACH-less transmission may be attempted in a configured amount of time. After the configured amount of time, a UE may be configured to fallback to performing legacy random access, i.e. random access with the RACH preamble.

[0349] Fallback to performing legacy random access may also be triggered by a UE receiving an indication of failure of a contention-resolution RACH-less transmission in a network response message. The indication may, for example, indicate that the UE is not synchronized, i.e. that any of UE GNSS location, NTN assistance information (partly comprising of the satellite ephemeris), estimation of a timing advance is inaccurate.

[0350] When re-attempting a contention-resolution RACH-less transmission, a UE may select new resources. When re-attempting a contention-resolution RACH-less transmission, a UE may use the same resources again. If the UE selects new resources, then an indication of where further contention-resolution RACH-less transmission contention-resolution RACH-less transmission instances are being re-transmitted needs to re-constructed. This may require that the MAC PDU is reconstructed.

[0351] The reconstruction of the MAC PDU may be done by the UE saving each constituent part of the MAC PDU before performing contention-resolution RACH-less transmission. For example, sub-PDU arriving from higher layers, for example via logical channel prioritization, is saved before constructing the sub PDU. All other sub PDUs may also be saved. Thus when the MAC PDU is reconstructed, the sub-PDUs that have been saved are reused along with, for example, a new MAC CE indicating the contention-resolution RACH-less transmission resources.

[0352] When a UE falls back to legacy random access, the UE may or may not be configured to include an indication of which contention-resolution RACH-less transmission resources were used. It may be, for example, that the PDU in the MAC layer is reconstructed and the indication of the resources is not included for legacy random access. The UE may also include an indication that a contention-resolution RACH-less transmission failed.

[0353] Move to a RRC_CONNECTED State

[0354] A UE may be configured or commanded to move to a RRC_CONNECTED state. This can be indicated in a network response message to the UE as part of MAC or a RRC message.

[0355] This can be due to either potentially a failure to parse the RRC message, or any other failure to deliver data etc., or it may be due to successful contention-resolution RACH-less transmission, but the network needing to continue UL or DL data transmission.

[0356] A UE may move to a RRC_CONNECTED state if the UE receives downlink data in a network response message that prompts the UE to send more data. The UE may wait for a specified time after having received the network response to see if the content of the response may trigger the UE to send more uplink data. The prompt may, for example, be a configurable timer, or a default time, such as 100 ms. Once the timer time runs out, the UE may move to a RRC IDLE state or a RRC inactive state.

[0357] Move to an RRC_IDLE State and an RRC_INACTIVE State

[0358] If a contention-resolution RACH-less transmission by a UE is successful and there is no more data to deliver, the UE may be configured to move back to, or remain in, a RRC IDLE state or a RRC inactive state, or any other non-connected RRC state.

[0359] In an example of the disclosure, there is provided a method for performing random access without Msg1 by a UE, the method comprising: transmitting, to a base station, a contention-based transmission; wherein transmitting the contention-based transmission comprises: selecting, from among a set of transmission resources in a transmission window configured for random access without Msg1, at least one transmission resource; and transmitting, in the selected transmission resource, the contention-based transmission; wherein the contention-based transmission comprises at least one of user plane data or control plane signalling.

[0360] In an example of the disclosure, there is provided the method of the first example, wherein the contention-based transmission comprises at least one of: a Msg3, and an RRC message.

[0361] In an example of the disclosure, there is provided the method of the second example, wherein the RRC message comprises at least one of: an RRC setup request, an RRC connection resume request, an RRC connection reestablishment request, and an RRC early data request.

[0362] In an example of the disclosure, there is provided the method of any one of the first to third examples, wherein the set of transmission resources for random access without Msg1 are configured by the network via broadcast.

[0363] In an example of the disclosure, there is provided the method of any one of the first to fourth examples, further comprising: monitoring, in a time window configured for a random access without Msg1 response, for a response from the base station.

[0364] In an example of the disclosure, there is provided the method of the fifth example, further comprising determining a RNTI to use for the monitoring, wherein the RNTI is calculated based on the transmission window.

[0365] In an example of the disclosure, there is provided the method of the fifth or sixth examples, wherein the response is a Msg4.

[0366] In an example of the disclosure, there is provided the method of any one of the fifth to seventh examples, wherein the Msg4 comprises an RRC message.

[0367] In an example of the disclosure, there is provided the method of the eighth example, wherein the RRC message comprises at least one of: an RRC connection setup message, an RRC connection resume message, an RRC connection reestablishment message, an RRC reject message, an RRC release message, and an RRC early data complete message.

[0368] In an example of the disclosure, there is provided the method of any one of the fifth to seventh examples, further comprising receiving the response in the time window.

[0369] In an example of the disclosure, there is provided the method of any one of the fifth to eighth examples, wherein the time window is configured to start a specified amount of time after the end of the transmission window.

[0370] In an example of the disclosure, there is provided the method of any of the first to eleventh examples, wherein the transmission window comprises a transmission frame.

[0371] In a thirteenth example, there is provided the method of any of the first to twelfth examples, wherein the set of transmission resources comprises a set of time slots; wherein selecting the at least one transmission resource comprises selecting, from among the set of time slots, at least one time slot; and wherein transmitting the contention-based transmission comprises transmitting the contention-based transmission in the selected at least one time slot.

[0372] In an example of the disclosure, there is provided the method of any of the first to thirteenth examples, wherein performing random access without Msg1 comprises performing contention-based early data transmission (EDT).

[0373] In an example of the disclosure, there is provided the method of any of the first to fourteenth examples, wherein the UE is included in a non-terrestrial network (NTN).

[0374] In an example of the disclosure, there is provided the method of the fifteenth example, wherein the UE is included in an internet of things (IoT) NTN.

[0375] In an example of the disclosure, there is provided a first network entity (e.g. a UE) configured to operate according to a method of any of the first to sixteenth examples.

[0376] In an example of the disclosure, there is provided a second network entity (e.g. a base station) configured to cooperate with a first network entity of the seventeenth example according to a method of any one of the first to sixteenth examples.

[0377] In an example of the disclosure, there is provided a network (e.g. a NTN, an IoT NTN) or wireless communication system comprising a first network entity according to the seventeenth example and a second network entity according to the eighteenth example.

[0378] In an example of the disclosure, there is provided a computer program comprising instructions which, when the program　is executed by a computer or processor, cause the computer or processor to carry out a method according to any one of the first to sixteenth examples.

[0379] In an example of the disclosure, there is provided a computer or processor-readable data carrier having stored thereon a computer program according to　the twentieth example.

[0380] By way of further explanation, examples of how the existing 3GPP standards might be modified in view of certain aspects of the present disclosure are provided. The skilled person will appreciate that any of the techniques provided in these examples may be applied in combination with any of the techniques described above and illustrated in the Figures.

[0381] Example 1

[0382] ------------------------ example based on 36.321 ------------------------

[0383] RACH-less Resource Indication MAC Control Element

[0384] The RACH-less resource indication MAC control element is identified by a MAC PDU subheader with LCID.

[0385] Figure 13 illustrates a RACH-less resource indication MAC control element according to an embodiment of the disclosure.

[0386] As referred to the Figure 13, the RACH-less resource indication MAC control element has a fixed size and consists of two octets defined as follows:

[0387] - F: This field indicates the slots or resources that the UE has transmitted in. The length of the field may be 12 bits.

[0388] - U: This field indicates the UE identity, which may be a randomly selected number. The length of the field may be 3 bits.

[0389] Figure 14 illustrates an example method for performing random access without Msg1 by a UE according to an embodiment of the disclosure.

[0390] In step 1402, the method comprises transmitting, to a base station, a contention-based transmission. Transmitting the contention-based transmission comprises, in step 1402a, selecting, from among a set of transmission resources in a transmission window configured for random access without Msg1, at least one transmission resource; and in step 1402b, transmitting, in the selected transmission resource, the contention-based transmission. The contention-based transmission comprises at least one of user plane data or control plane signalling.

[0391] Figure 15 is a block diagram of an exemplary network entity (e.g. UE or base station) that may be used in examples of the present disclosure according to an embodiment of the disclosure.

[0392] The skilled person will appreciate that the network entity illustrated in Figure 15 may be implemented, for example, as a network element on a dedicated hardware, as a software instance running on a dedicated hardware, or as a virtualised function instantiated on an appropriate platform, e.g. on a cloud infrastructure.

[0393] The network entity 1500 comprises a processor 1501 (or controller), a transmitter 1503 and a receiver 1505. The receiver 1505 is configured for receiving one or more messages from one or more other network entities. The transmitter 1503 is configured for transmitting one or more messages to one or more other network entities. The processor 1501 is configured for performing operations as described above.

[0394] The terms and words used herein are not limited to the bibliographical or standard meanings, but, are merely used to enable a clear and consistent understanding of the examples disclosed herein.

[0395] Throughout the description and claims, the words "comprise", "contain" and "include", and variations thereof, for example "comprising", "containing" and "including", means "including but not limited to", and is not intended to (and does not) exclude other features, elements, components, integers, steps, processes, functions, characteristics, and the like.

[0396] Throughout the description and claims, the singular form, for example "a", "an" and "the", encompasses the plural unless the context otherwise requires. For example, reference to "an object" includes reference to one or more of such objects.

[0397] Throughout the description and claims, language in the general form of "X for Y" (where Y is some action, process, function, activity or step and X is some means for carrying out that action, process, function, activity or step) encompasses means X adapted, configured or arranged specifically, but not necessarily exclusively, to do Y.

[0398] Features, elements, components, integers, steps, processes, functions, characteristics, and the like, described in conjunction with a particular aspect, embodiment, example or claim are to be understood to be applicable to any other aspect, embodiment, example or claim disclosed herein unless incompatible therewith.

[0399] While the invention has been shown and described with reference to certain examples, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the scope of the invention, as defined by the appended claims.

[0400] The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and / or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. The phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the scope of the embodiments as described herein.

[0401] While the disclosure has been described with reference to various embodiments, various changes may be made without departing from the spirit and the scope of the present disclosure, which is defined, not by the detailed description and embodiments, but by the appended claims and their equivalents.

Claims

1.A method performed by a terminal in a wireless communication system, the method comprising:receiving, from a base station, configuration information on transmission resources to be used for a random access channel (RACH)-less transmission;determining a resource among the transmission resources;transmitting, to the base station, a message 3 of a random access procedure based on the resource, the message 3 including uplink data for early data transmission (EDT); andreceiving, from the base station, a message 4 of the random access procedure, as a response of the message 3.2.The method of claim 1,wherein the configuration information is received via a broadcast signaling,wherein the transmission resources are located within a transmission window,wherein the resource includes a plurality of time resources selected for a contention resolution with another terminal, andwherein the uplink data for EDT is repeatedly transmitted based on the plurality of time resources.3.The method of claim 2, further comprising:determining a radio network temporary identifier (RNTI) based on the transmission window, andwherein the RNTI is used for monitoring the message 4.4.The method of claim 3,wherein monitoring the message 4 is started at a specific time after the transmission window.5.A method performed by a base station in a wireless communication system, the method comprising:transmitting, to a terminal, configuration information on transmission resources to be used for a random access channel (RACH)-less transmission;receiving, from the terminal, a message 3 of a random access procedure based on a resource among the transmission resources, the message 3 including uplink data for early data transmission (EDT); andtransmitting, to the terminal, a message 4 of the random access procedure, as a response of the message 3.6.The method of claim 5,wherein the configuration information is transmitted via a broadcast signaling,wherein the transmission resources are located within a transmission window,wherein the resource includes a plurality of time resources selected for a resolution of a contention with at least one of other terminals, andwherein the uplink data for EDT is received based on at least one of the plurality of time resources.7.The method of claim 6, further comprising:decoding the uplink data for EDT based on a first resource where the contention is not detected, the first resource among the at least one of the plurality of time resources;removing a contribution of the uplink data from a second resource where the contention is detected, the second resource among the at least one of the plurality of time resources; anddecoding uplink data transmitted from the at least one of other terminals based on the other resource.8.A terminal in a wireless communication system, the terminal comprising:a transceiver;a processor communicatively coupled to the transceiver; andmemory, communicatively coupled to the processor, storing instructions executable by the processor to cause the terminal to:receive, from a base station, configuration information on transmission resources to be used for a random access channel (RACH)-less transmission,determine a resource among the transmission resources,transmit, to the base station, a message 3 of a random access procedure based on the resource, the message 3 including uplink data for early data transmission (EDT), andreceive, from the base station, a message 4 of the random access procedure, as a response of the message 3.9.The terminal of claim 8,wherein the configuration information is received via a broadcast signaling,wherein the transmission resources are located within a transmission window,wherein the resource includes a plurality of time resources selected for a contention resolution with another terminal, andwherein the uplink data for EDT is repeatedly transmitted based on the plurality of time resources.10.The terminal of claim 9,wherein the instruction executable by the processor further cause the terminal to determine a radio network temporary identifier (RNTI) based on the transmission window, andwherein the RNTI is used for monitoring the message 4.11.The terminal of claim 10,wherein monitoring the message 4 is started at a specific time after the transmission window.12.A base station in a wireless communication system, the base station comprising:a transceiver;a processor communicatively coupled to the transceiver; andmemory, communicatively coupled to the processor, storing instructions executable by the processor to cause the base station to:transmit, to a terminal, configuration information on transmission resources to be used for a random access channel (RACH)-less transmission,receive, from the terminal, a message 3 of a random access procedure based on a resource among the transmission resources, the message 3 including uplink data for early data transmission (EDT), andtransmit, to the terminal, a message 4 of the random access procedure, as a response of the message 3.13.The base station of claim 12,wherein the configuration information is transmitted via a broadcast signaling,wherein the transmission resources are located within a transmission window,wherein the resource includes a plurality of time resources selected for a resolution of a contention with at least one of other terminals, andwherein the uplink data for EDT is received based on at least one of the plurality of time resources.14.The base station of claim 13,wherein the instructions further cause the base station to:decode the uplink data for EDT based on a first resource where the contention is not detected, the first resource among the at least one of the plurality of time resources,remove a contribution of the uplink data from a second resource where the contention is detected, the second resource among the at least one of the plurality of time resources, anddecode uplink data transmitted from the at least one of other terminals based on the other resource.

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