Method, device and system for coverage enhancement for NTN networks

Abstract

A method performed by a user equipment, UE, for coverage enhancement for a non-terrestrial network, NTN, comprising: receiving a predetermined timer value from a network node of the NTN; sending an access request to the network node to start a random access, RA, procedure; initiating a timer of the UE when starting the RA procedure; determining whether the RA procedure in a first coverage enhancement level is successful; and performing a coverage enhancement level switch in response to the failure of the RA procedure in the first coverage enhancement level after the timer exceeding the predetermined timer value.

Description

[0001] 202405302

[0002] 1

[0003] METHOD, DEVICE AND SYSTEM FOR COVERAGE ENHANCEMENT FOR NTN NETWORKS

[0004] BACKGROUND

[0005] The use of Internet of Things (loT) devices in non-terrestrial networks (NTN), such as satellite communication systems, is increasing. These networks are expected to support a wide range of device types and operate under diverse signal and coverage conditions. Due to the long distance between the network node of the NTN and the devices on earth, the coverage scope of the network node is large, which could cover a large number of devices. As the number of connected devices grows, various technical challenges related to network access and device connectivity have emerged in NTN environments.

[0006] A range of approaches have been explored in terrestrial networks to address connection issues. However, the unique characteristics of NTN environments present additional technical challenges. As NTN technologies continue to evolve and the number of connected loT devices grows, addressing the specific requirements and operational conditions of non-terrestrial networks remains an area of ongoing technical interest.

[0007] SUMMARY

[0008] According to a first aspect of the present disclosure, a method performed by a user equipment (UE) for coverage enhancement for a non-terrestrial network (NTN) is provided. The method includes: receiving a predetermined timer value from a network node of the NTN; sending an access request to the network node to start a random access (RA) procedure; initiating a timer of the UE when starting the RA procedure; determining whether the RA procedure in a first coverage enhancement level is successful; and performing a coverage enhancement level switch in response to the failure of the RA procedure in the first coverage enhancement level after the timer exceeding the predetermined timer value. For satellite-based communications, due to large distance between the satellites and the devices on the earth, the beams can become very wide. Thus, cell coverage spans many dozens of kms for LEO (Low Earth Orbit) satellites and may even span hundreds of kms for GSO (Geosynchronous Orbit) satellites. Due to 202405302

[0009] 2 large coverage per satellite beam, and the exploding number of devices with varying capabilities and categories, the number of devices per beam may be very large. This amounts to very limited resource availability per device in NTN networks. NTN networks already support loT operation, based upon NB-loT and MTC devices. Rel-19 has in its objective the support for NR based RedCap devices. This trend leads to a large number of devices, many thousands per sq km present in the coverage of a satellite beam. This amounts to very limited resource availability per device in NTN networks. Furthermore, the network experiences higher congestion, collision, and performance degradation while the UE’s initiate conventional coverage enhancements.

[0010] The method of the first aspect can provide a relaxed coverage enhancement to reduce the RACH (Random Access Channel) congestion in NTN networks. The relaxed coverage enhancement method is a more general and flexible coverage enhancement (CE) method compared with conventional CE method. The network configures a new timer for the UE to switch from current coverage enhancement (CE) level to the next CE level. By employing multi-level coverage enhancement and timer-based control, the solution enables dynamic adjustment of the randomaccess (RA) process, leading to more reliable and efficient network access for a large number of devices under challenging coverage conditions. The effects of the present disclosure include improved random-access success rate for loT devices in NTN environments, alleviation of RACH congestion, enhanced utilization of network resources, reduced device energy consumption, and increased network robustness. Furthermore, this application could also achieve capacity enhancement to some extent. While its mechanisms, such as timer-based control and dynamic CE level switching, can alleviate access congestion and improve resource utilization — thus contributing to access capacity.

[0011] In an embodiment of the first aspect, the method may further include: after determining whether the RA procedure in the first coverage enhancement level is successful, discarding the timer when the RA procedure in the first coverage enhancement level is successful; and establishing a connection between the UE and the network node.

[0012] In a further embodiment of the first aspect, the UE performing a coverage enhancement level switch in response to the failure of the RA procedure after the timer exceeding the predetermined timer value may include: waiting for the timer 202405302

[0013] 3 to exceed the predetermined timer value; and switching to a second coverage enhancement level from the first coverage enhancement level.

[0014] Preferably, the timer is initiated when the UE starts RA procedure. The timer functions as follows. If the RA procedure is successful, the timer is discarded. Else, the UE wait for the timer to expire before switching to the next CE level. In an embodiment of the first aspect, the UE performing a coverage enhancement level switch in response to the failure of the RA procedure after the timer exceeding the predetermined timer value may include: waiting for the timer to exceed the predetermined timer value when a first attempt of the RA procedure fails; performing a second attempt of the RA procedure after the timer exceeding the predetermined timer value; determining whether the second attempt of the RA procedure is successful; and switching to a second coverage enhancement level from the first coverage enhancement level when the second attempt of the RA procedure is not successful.

[0015] Preferably, the timer is initiated when the UE starts RA procedure. The timer functions as follows. If the RA procedure is successful, the timer is discarded. Else, the UE waits for the timer to expire and re-try at the same CE level. If still RA fails, the UE switches to the next CE level.

[0016] In an embodiment of the first aspect, the method may further include: establishing a connection between the UE and the network node when the second attempt of the RA procedure is successful.

[0017] The UE can get an additional opportunity to use the same CE level, if RA is successful in the same CE level, the network congestion is reduced, and the UE will save energy.

[0018] In a further embodiment of the first aspect, the method may further include: receiving the predetermined timer value from the network node via a system information block, SIB, message and / or a radio resource control, RRC, reconfiguration message.

[0019] The network node, for example, gNB, eNB, base station, can broadcast the timer values via SIB, RRC reconfiguration message to prevent a large number of UEs from simultaneously switching CE levels or retrying access attempts, which could otherwise lead to severe congestion and collision on the RACH channel. By spacing out access attempts and CE level transitions, the timer mechanism can smooth network load, reduces unnecessary retries, improves resource utilization, 202405302

[0020] 4 and enhances both network robustness and user experience. Further, after receiving the timer values from the network, the UE may restrict the CE level switch in case of RACH failure in the current CE level to avoid collisions or network congestions with frequent CE level switch. The timer acts as a buffer to provide an opportunity for the UE to access the network before finally switching the CE level; which will lead to higher power consumption and reduced battery life.

[0021] In a further embodiment of the first aspect, the UE may be any of a narrowband internet of things (NB-loT) device, reduced capability (RedCap) device, and a machine-type communication (MTC) device compliant with NTN-loT standards. The application scenario of the present disclosure can be for example the initial network access or random access of large numbers of loT devices — such as NB- loT, RedCap and other types of MTC terminals — in non-terrestrial network (NTN) environments, including satellite and high-altitude platform systems. It is suitable in particular for situations involving weak coverage, high path loss, extended propagation delay, and high device density, where conventional access mechanisms may lead to congestion and low random-access success rates. Typical use cases can include remote monitoring, smart metering, and wide-area loT deployments in rural, remote, or underserved regions.

[0022] In an embodiment of the first aspect, the step of performing a coverage enhancement level switch is repetitive until a predetermined condition is met. As previously mentioned, the UE could for example switch from the first CE level to the second CE level. It should be understood that the specific embodiments described herein are merely illustrative of the present disclosure and are not intended to limit the present disclosure. The ordinal numbers “first” “second” are used to distinguishing different CE levels. However, they do not refer to specific CE levels. The first and second CE level may refer to any CE level in the NTN environment. Furthermore, the CE level switch may be repeated multiple times until a predetermined condition is satisfied. This could achieve a balance between saving radio resources and coverage / capacity enhancement.

[0023] In an embodiment of the first aspect, the predetermined condition may include any of:

[0024] (1) establishing a connection between the UE and the network node after the coverage enhancement level switch; and / or 202405302

[0025] 5

[0026] (2) reaching to a highest coverage enhancement level in the NTN; and / or

[0027] (3) reaching to a predetermined number of the coverage enhancement level switch; and / or

[0028] (4) the UE reaching to a predetermined battery level.

[0029] The predetermined conditions can be set manually or automatically according to needs. Multiple conditions can coexist and are monitored in parallel. The CE level switching and repetition process is terminated as soon as any one of the defined conditions are met. Such design can improve the flexibility and robustness of the NTN environment, making it adaptable to various practical scenarios.

[0030] According to a second aspect of the present disclosure, a method, performed by a network node for coverage enhancement (CE) for a non-terrestrial network (NTN) is provided. The method includes: broadcasting a predetermined timer value to one or more user equipment (UE) with a timer, wherein the one or more UE is configured to perform a coverage enhancement level switch when a random access (RA) procedure fails after the timer exceeding the predetermined timer value; and establishing a connection with any of the one or more UE with a successful RA attempt.

[0031] In an embodiment of the second aspect, the broadcasting a predetermined timer value to one or more user equipment (UE) with a timer may include: broadcasting the predetermined timer value via a system information block, SIB, message and / or a radio resource control, RRC, reconfiguration message.

[0032] In an embodiment of the second aspect, the NTN may support internet of things (loT) operation.

[0033] According to a third aspect of the present disclosure, a user equipment (UE) includes: a receiving module configured to receive a predetermined timer value from a network node of a non-terrestrial network, NTN; a sending module configured to send an access request to the network node to start a random access, RA, procedure; a timing module configured to initiate a timer of the UE when starting the RA procedure; a determining module configured to determine whether the RA procedure in a first coverage enhancement level is successful; and a switching module configured to perform a coverage enhancement level switch in response to the failure of the RA procedure in the first coverage enhancement level after the timer exceeding the predetermined timer value. In an embodiment of the third aspect, the UE may be any of a narrowband internet 202405302

[0034] 6 of things (NB-loT) device, reduced capability (RedCap) device, and a machinetype communication (MTC) device compliant with NTN-loT standards.

[0035] According to a fourth aspect of the present disclosure, a system for coverage enhancement for a non-terrestrial network (NTN) includes: one or more user equipment, UE, configured to perform methods of the first aspect; and a network node configured to perform methods of any of the second aspect.

[0036] These and other features, aspects, and advantages will be apparent from a reading of the following detailed description and a review of the associated drawings. It is to be understood that both the foregoing general description and the following detailed description are explanatory and do not restrict aspects as claimed.

[0037] BRIEF DESCRIPTION OF THE DRAWINGS

[0038] The present disclosure is further described in terms of exemplary embodiments. These exemplary embodiments are described in detail with reference to the drawings. The drawings are not drawn to scale. These embodiments are nonlimiting exemplary embodiments, in which like reference numerals represent similar structures throughout the several views of the drawings, and wherein: FIG. 1 is a schematic diagram illustrating an exemplary NTN environment 100 according to some embodiments of the present disclosure;

[0039] FIG. 2 is a schematic diagram illustrating coverage enhancement 200 according to some embodiments of the present disclosure;

[0040] FIG. 3a is a flowchart illustrating an exemplary process 3100 performed by the UE for coverage enhancement in the NTN according to some embodiments of the present disclosure;

[0041] FIG. 3b is a flowchart illustrating an exemplary process 3200 performed by the network node for coverage enhancement in the NTN according to some embodiments of the present disclosure;

[0042] FIG. 4a is a flowchart illustrating another exemplary process 4100 performed by the UE for coverage enhancement in the NTN according to some embodiments of the present disclosure;

[0043] FIG. 4b is a flowchart illustrating another exemplary process 4200 performed by the network node for coverage enhancement in the NTN according to some embodiments of the present disclosure; 202405302

[0044] 7

[0045] FIG. 5a is a flowchart illustrating another exemplary process 5100 performed by the UE for coverage enhancement in the NTN according to some embodiments of the present disclosure;

[0046] FIG. 5b is a flowchart illustrating another exemplary process 5200 performed by the network node for coverage enhancement in the NTN according to some embodiments of the present disclosure;

[0047] FIG. 6 is a block diagram illustrating an exemplary user equipment 600 according to some embodiments of the present disclosure.

[0048] DETAILED DESCRIPTION

[0049] The following description is presented to enable any person skilled in the art to make and use the present disclosure and is provided in the context of a particular application and its requirements. Various modifications to the disclosed embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be applied to other embodiments and applications without departing from the spirit and scope of the present disclosure. Thus, the present disclosure is not limited to the embodiments shown but is to be accorded the widest scope consistent with the claims.

[0050] The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting. As used herein, the singular forms “a,” “an,” and “the” may be intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprise,” “comprises,” and / or “comprising,” “include,” “includes,” and / or “including,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0051] These and other features, and characteristics of the present disclosure, as well as the methods of operation and functions of the related elements of structure and the combination of portions and economies of manufacture, may become more apparent upon consideration of the following description with reference to the accompanying drawings, all of which form a part of this disclosure. It is to be expressly understood, however, that the drawings are for the purpose of illustration and description only and are not intended to limit the scope of the 202405302

[0052] 8 present disclosure. It is understood that the drawings are not to scale.

[0053] The flowcharts used in the present disclosure illustrate operations that systems implement according to some embodiments of the present disclosure. It is to be expressly understood, the operations of the flowchart may be implemented not in order. Conversely, the operations may be implemented in inverted order, or simultaneously. Moreover, one or more other operations may be added to the flowcharts. One or more operations may be removed from the flowcharts.

[0054] In order to make the purpose, technical solution, and advantages of the present disclosure clearer, the present disclosure will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present disclosure and are not intended to limit the present disclosure.

[0055] The present disclosure concerns NTN-loT (Non-Terrestrial Network Internet of Things), capacity / coverage enhancements, radio resources and gNB signaling. In NTN networks, due to the large coverage per satellite beam, and the exploding number of devices with varying capabilities and categories, the number of devices per beam may be very large. This amounts to very limited resource availability per device in NTN networks. There is a need to reduce the RACH congestion in NTN networks. The network configures a new timer for the UE to switch from current CE level to the next CE level. The proposed solution can reduce the network overload and improve effective use of resources and also reduce energy consumption at the UE. This solution is highly relevant to 3GPP systems, including but not limited to systems beyond 5G and / or 6G, as well as applications in the continental and automotive sectors.

[0056] FIG. 1 is a schematic diagram illustrating an exemplary NTN environment 100 according to some embodiments of the present disclosure. The network node in FIG.1 is satellite 110. The satellite 110 operates at an elevation angle of approximately 30 degrees. As shown, satellite 110 is capable of generating multiple spot beams, each covering a distinct geographic area on the Earth's surface. The overall coverage area, referred to as the satellite footprint, is partitioned into a plurality of beam footprints. Each beam footprint corresponds to a potential service area for NTN connectivity.

[0057] At a given time instance, denoted as Snapshot-i, a subset of the beam footprints 131-1 to 131-n are actively illuminated by the satellite, as indicated by the shaded 202405302

[0058] 9

[0059] (illuminated, solid line) regions. These illuminated beam footprints represent areas where the NTN service is currently available, and are associated with active beams, such as active beam-1 121 -1 and active beam-N 121 -n.

[0060] The remaining beam footprints are depicted as solid-line 132-1 to 132-n or dashed-line regions 133-1 to 133-n that are not illuminated by an active beam at the given time. In served beam footprints 132-1 to 132-n, the NTN service is available, but not currently illuminated by an active beam in this snapshot. In unserved beam footprints 133-1 to 133-n, the NTN service is not available.

[0061] The satellite footprints can be up to several million km2. Each physical / active beam transmitted by a satellite can cover a beam footprint of thousands of km2. Thus, coverage enhancement and capacity enhancements play a key role in NTN. However, the following challenges exist:

[0062] (1 ) Wide Beams in Satellites:

[0063] For satellite-based communications, due to large distance between the satellites and the devices on the earth, the beams become very wide. Thus, cell coverage spans many dozens of kms for LEO and may even span hundreds of kms for GSO.

[0064] (2) Large Number of UEs per Beam:

[0065] Due to large coverage per satellite beam, and the exploding number of devices with varying capabilities and categories, the number of devices per beam may be very large. This amounts to very limited resource availability per device in NTN networks.

[0066] (3) Support of Low-cost loT Type of Devices:

[0067] NTN networks already support loT operation, based upon NB-loT and MTC devices. Rel-19 has in its objective the support for NR based RedCap devices. This trend leads to a large number of devices, many thousands per sq km present in the coverage of a satellite beam.

[0068] (4) Spectrum Scarcity:

[0069] Although NTN is supporting new device categories and new device types, the spectrum available for these devices is not scaling up. Thus, to avoid spectrum being bottleneck for communication in NTN, the devices need to be simultaneously supported for UL (uplink) transmissions which is one of the major use cases in NTN.

[0070] CE is achieved through repetition in time, retransmission, and power-boosting in- 202405302

[0071] 10 band and guard band operating modes. The coverage extension feature of NB-loT is handy when the sensors are located in remote or challenging areas. Reliable coverage enhancement is achieved by the repeated transmission of data and control signaling. Each transmission can be configured to repeat for a designated number of times in order to ensure high success opportunities at the desired coverage level. The present disclosure can provide the relaxed coverage enhancement method for NTN networks to achieve higher success opportunities at the same coverage level before switching to the next coverage level.

[0072] FIG.2 is a schematic diagram illustrating coverage enhancement 200 according to some embodiments of the present disclosure. A coverage area 210 is divided into multiple concentric regions 210-0 to 210-2, each corresponding to a different coverage enhancement (CE) level, such as CEO 210-0, CE1 210-1 and CE2 210- 2. Devices located closer to the center of the coverage area experiences lower path loss and higher received power, and are associated with CEO. Devices located farther from the center, toward the edge of the coverage area, experience higher path loss and lower received power, and are associated with higher CE levels, such as CE1 and CE2. An inset graph is provided to show the relationship between power level and path loss. As path loss increases, the received power decreases.

[0073] For each CE level, a corresponding number of transmission repetitions is indicated. Devices in CEO require fewer repetitions for successful communication, while devices in CE1 and CE2 require progressively more repetitions to compensate for increased path loss and reduced received power. The number of repetitions increases with the CE level, as illustrated by the horizontal bars aligned with each CE region.

[0074] The number of repetition value is directly proportional to Maximum Coupling Loss (MCL). Number of repetitions will improve the SNR (Signal-to-Noise Ratio) at the receiver. Increase in number of repetitions results in increase in energy consumption. Large repetition number results in higher latency. Conventional CE will result in radio resource wastage (UE occupies a channel for longer duration in case of higher-level CE). CE is suitable for latency insensitive applications (applications that can tolerate 10 seconds of transmission delay). Avoiding CE upgradation with any alternative can improve energy efficiency and reduce radio resource wastage. Thus, an intelligent, dynamic, and on-demand CE level switch 202405302

[0075] 11 method is needed.

[0076] In some embodiments, CE Operation is categorized into four different levels.

[0077] These four groups are divided into two groups and each of the groups belongs to two different Operation Mode as below.

[0078] Each of the level differs mostly in RACH and Paging process. Some of the major differences with different CE levels are:

[0079] RACH configuration and resources (e.g, frequency, time, preamble) associated with each of the RACH configuration;

[0080] Frequency resources used for RACH transmission;

[0081] Repetition Number for RACH Preamble.

[0082] The use of repetitions for PUSCH (Physical Uplink Shared Channel) performance is important in NB-loT NTN deployment scenarios. Without optimization, large code lengths and concurrent transmissions can severely degrade performance, leading to diminished capacity gains and poorer link-level quality. Addressing these issues will be important to maintain a robust and efficient network. The present disclosure provides a relaxed coverage enhancement method to ensure a reliable network, in particular, reduce the RACH congestion in NTN networks.

[0083] FIG. 3a is a flowchart illustrating an exemplary process 3100 performed by the UE for coverage enhancement in the NTN according to some embodiments of the present disclosure. The network configures a new timer for the UE to switch from current CE level to the next CE level. The timer is initiated when the UE starts the RA procedure. When the RA procedure fails, the UE performs CE level switch according to the timer.

[0084] The non-terrestrial network (NTN) refers to a wireless communication system in which at least a portion of the network infrastructure is implemented using non- 202405302

[0085] 12 terrestrial platforms, such as satellites (e.g., LEO, MEO, GEO satellites) or high- altitude platform stations (HAPS). The NTN is configured to provide wireless connectivity to user equipment (UE) located within a coverage area that may extend over wide geographic regions, including remote or underserved locations where terrestrial infrastructure may be limited or unavailable.

[0086] The user equipment (UE) may comprise any device capable of wireless communication with the NTN, including but not limited to a narrowband internet of things (NB-loT) device, reduced capability (RedCap) device, and a machine-type communication (MTC) device compliant with NTN-loT standards. In some embodiments, the UE may also include HTC (human type communication) device. The network node may include but not be limited to a satellite payload, a high- altitude platform, a gateway, a gNB (next-generation NodeB, i.e. , 5G base station), an eNB (evolved NodeB, i.e., 4G base station), or any other suitable access point or controller. The network node is operative to manage network access, broadcast or signal configuration parameters (such as timer values or CE level information), and coordinate resource allocation for UEs within the NTN coverage area.

[0087] In 3110, the UE receives a predetermined timer value from a network node of the NTN. The predetermined timer value may be provided to the UE via broadcast signaling from the network node, such as through a System Information Block (SIB), or via dedicated signaling, such as a Radio Resource Control (RRC) message, depending on the operational state of the UE. The timer value may be associated with a coverage enhancement (CE) level and is utilized by the UE to control the timing of subsequent access attempts or CE level switching procedures. By receiving the predetermined timer value from the network node, the UE is able to coordinate its access behavior in accordance with network policies and resource management strategies, thereby facilitating efficient and reliable network access in NTN environments.

[0088] In some embodiments, when there are many UEs in the NTN network, the UEs may receive same timer values from the network node. It can be used in scenarios where network conditions are relatively uniform, or where simplicity and reduced signaling overhead are desired.

[0089] In some embodiments, when there are many UEs in the NTN network, the UEs may receive different values. For example, the network may associate distinct 202405302

[0090] 13 timer values with different CE levels, device types, or service categories. In some cases, the network node may configure and broadcast or signal different timer values for different CE levels, such that each CE level (e.g., CE level 0, CE level 1 , CE level 2) has a corresponding timer value. The association between the timer value and the CE level enables the UE to apply a distinct timing control for access attempts or CE level switching procedures, depending on the current CE level in which the UE is operating. It is useful for optimizing access control and resource management in NTN and loT scenarios, where devices may experience widely different path loss and congestion levels.

[0091] By way of illustration, the timer value for a lower CE level (e.g., CE level 0, corresponding to devices experiencing low path loss and high received power) may be set to a relatively short duration, allowing for more frequent access attempts or quicker transitions. Conversely, the timer value for a higher CE level (e.g., CE level 2, corresponding to devices experiencing high path loss and low received power) may be set to a longer duration, thereby spacing out access attempts to reduce network congestion and avoid excessive resource consumption.

[0092] In 3120, the UE sends an access request to the network node to start a random access, RA, procedure. The user equipment (UE) initiates a random access (RA) procedure by transmitting an access request to a network node. The access request may be transmitted via a physical random-access channel (PRACH) and may include a randomly selected preamble or other identifier. Upon transmission of the access request, the UE seeks to establish communication with the network node, thereby enabling subsequent signaling and resource allocation.

[0093] In 3130, the UE initiates a timer of the UE when starting the RA procedure. The timer may be started concurrently with, or immediately prior to, the transmission of an access request to a network node. The timer is configured to track a predetermined duration associated with the RA procedure, such that expiration of the timer may trigger a subsequent action by the UE, for example, initiating a retry, or transitioning to a different coverage enhancement (CE) level. By initiating the timer at the start of the RA procedure, the UE is able to manage the timing and control of access attempts in accordance with network parameters and operational requirements.

[0094] In 3140, the UE determines whether the RA procedure in a first coverage 202405302

[0095] 14 enhancement level is successful. The determination may be based on whether the UE receives an expected response, such as a random-access response (RAR) message, from a network node within a predetermined time window following initiation of the RA procedure. If the expected response is received within the specified time period, the UE may determine that the RA procedure in the first CE level is successful. Conversely, if the expected response is not received within the predetermined time window, the UE may determine that the RA procedure in the first CE level is unsuccessful and may proceed to initiate a subsequent action, such as retrying the RA procedure or transitioning to a different CE level. In some embodiments, after determining whether the random access (RA) procedure in the first coverage enhancement (CE) level is successful, the user equipment (UE) is configured to discard the timer upon determining that the RA procedure in the first CE level is successful. Discarding the timer may include stopping and / or resetting the timer, thereby preventing any further timer-based actions related to the RA attempt. Subsequently, the UE proceeds to establish a connection with the network node. Establishing the connection may include performing one or more signaling exchanges with the network node, such as completing a radio resource control (RRC) connection setup or other protocol procedures, thereby enabling the UE to transition to a connected state and commence further communication with the network node.

[0096] In 3150, the UE performs a coverage enhancement level switch in response to the failure of the RA procedure in the first coverage enhancement level after the timer exceeding the predetermined timer value. In an example, the UE may perform the CE level switch after the timer expires. In another example, the UE may retry the same CE level after the timer expires. Then, the UE can perform the CE level switch after the subsequent attempt fails. FIGs. 4 and 5 discuss these two situations in detail.

[0097] In some embodiments, a coverage enhancement (CE) level switch refers to a process by which the user equipment (UE) transitions from a current CE level to a different CE level in response to the failure of a random access (RA) procedure after the expiration of a timer. The CE level switch may be performed in a variety of ways. For example, the CE level switch may involve incrementally moving from a lower CE level to the next higher CE level (e.g., from CE level 0 to CE level 1 , or from CE level 1 to CE level 2). In some cases, The CE level switch may also be 202405302

[0098] 15 performed in the reverse direction. Alternatively, the CE level switch may involve transitioning from the current CE level to any other CE level, which may be determined based on network configuration, device capability, or other criteria. The ability to switch between CE levels in a flexible manner allows the UE to adapt its access strategy to varying coverage conditions and network requirements, thereby improving the likelihood of successful network access and optimizing resource utilization.

[0099] In some embodiments, the step of preforming a coverage enhancement level switch 3150 is repetitive until a predetermined condition is met. The user equipment (UE) may repeatedly transition between different CE levels — such as incrementally moving from a lower CE level to a higher CE level, or vice versa, or from a current CE level to a different CE level — based on the outcome of random access (RA) procedures and other operational factors. The repetitive nature of the CE level switching enables the UE to dynamically adapt to varying network conditions, coverage scenarios, and device states, thereby improving the likelihood of successful network access and optimizing resource utilization.

[0100] The predetermined condition may include but not limited to:

[0101] (1 ) establishing a connection between the UE and the network node after the coverage enhancement level switch; and / or

[0102] (2) reaching to a highest coverage enhancement level in the NTN; and / or

[0103] (3) reaching to a predetermined number of the coverage enhancement level switch; and / or

[0104] (4) the UE reaching to a predetermined battery level.

[0105] In one example, the repetitive CE level switching process may be terminated when the UE successfully establishes a connection with the network node, such as by receiving a response from the network node, completing a radio resource control (RRC) connection setup or other access procedure.

[0106] In another example, the process may be terminated when the UE reaches the maximum allowable CE level defined for the non-terrestrial network (NTN), beyond which no further CE level switching is permitted. When the UE reaches the maximum allowable CE level defined for the non-terrestrial network (NTN), the UE may continue to perform multiple repetitions of the random access procedure at that CE level. The UE may repeat access attempts at the highest CE level, subject to a maximum number of retries or other termination conditions, until 202405302

[0107] 16 successful access is achieved or the process is otherwise terminated.

[0108] In another example, the process may be terminated when the number of CE level switches performed by the UE reaches a predefined threshold, thereby limiting the number of attempts and preventing excessive resource consumption.

[0109] In another example, the process may be terminated if the UE’s battery level falls below a specified threshold, thereby conserving energy and preventing further access attempts under low-power conditions. As an example, the process may be terminated if the user equipment (UE) autonomously determines that its battery level has fallen below a specified threshold. In this case, the UE may cease further CE level switching or access attempts in order to conserve energy and preserve device longevity, especially in low-power scenarios. As another example, in addition to timer-based control, the network node (e.g., gNB) may broadcast a mapping of repetition values associated with different battery level ranges. The UE may select an appropriate repetition value for access attempts based on its current battery level, as indicated by the mapping received from the network node. This approach allows the network to adaptively manage access reliability and energy consumption, such that UEs with higher battery levels may use more repetitions for increased reliability, while UEs with lower battery levels may use fewer repetitions to conserve energy. The mapping may be provided via system information broadcast and may be used in conjunction with timer-based mechanisms for optimal access control.

[0110] FIG. 3b is a flowchart illustrating an exemplary process 3200 performed by the network node for coverage enhancement in the NTN according to some embodiments of the present disclosure. The network node may include but not limited to a satellite payload, a high-altitude platform, a gateway, a gNB (nextgeneration NodeB, i.e. , 5G base station), an eNB (evolved NodeB, i.e. , 4G base station), or any other suitable access point or controller. The network node is operative to manage network access, broadcast or signal configuration parameters (such as timer values or CE level information), and coordinate resource allocation for UEs within the NTN coverage area.

[0111] In 3210, the network node broadcasts a predetermined timer value to one or more UE with a timer, wherein the one or more UE is configured to perform a coverage enhancement level switch when a RA procedure fails after the timer exceeding the predetermined timer value. The predetermined timer value may be broadcast by a 202405302

[0112] 17 network node, for example, via system information signaling. Each UE is configured to initiate the timer upon commencement of a random access (RA) procedure. If the RA procedure fails and the timer exceeds the predetermined timer value, the UE is further configured to perform a coverage enhancement (CE) level switch. This approach facilitates efficient management of network access attempts, reduces the likelihood of simultaneous access collisions, reduce RACH congestion, and helps to balance network load.

[0113] In some embodiments, the network node is configured to broadcast the predetermined timer value to one or more user equipment (UE) via a system information block (SIB) message and / or a radio resource control (RRC) reconfiguration message. The SIB message may be used to convey the timer value to all UEs within the coverage area prior to connection establishment, thereby enabling each UE to apply the timer value during initial access procedures. Furthermore, the timer can be used for subsequent RACH after first setup. In this case, the timer could be set via RRC reconfiguration.

[0114] In 3220, a connection is established between any of the one or more UE that have successfully completed the RA procedure and the network node. The process may include the UE initiating a random access (RA) procedure, receiving a response from the network node, and completing a series of signaling exchanges — such as radio resource control (RRC) messages — required to establish a dedicated communication link. Upon successful completion of these procedures, the UE and the network node are able to exchange data and control information over an established connection, thereby enabling reliable and efficient communication in the NTN.

[0115] In some embodiments, the non-terrestrial network (NTN) is configured to support Internet of Things (loT) operation. The NTN provides wireless connectivity specifically adapted for loT applications, enabling communication with a large number of low-power, low-cost, and diverse loT terminals. The network infrastructure, which may include satellites or other non-terrestrial platforms, is designed to accommodate the connectivity, scalability, and coverage requirements characteristic of loT deployments. By supporting loT operation, the NTN facilitates reliable network access, data transmission, and device management for loT devices across wide geographic areas, including remote or underserved locations. 202405302

[0116] 18

[0117] FIG. 4a is a flowchart illustrating another exemplary process 4100 performed by the UE for coverage enhancement in the NTN according to some embodiments of the present disclosure. The timer is initiated when the UE starts RA procedure. The timer functions as follows:

[0118] 1. If the RA procedure is successful, the timer is discarded.

[0119] 2. Else, the UE wait for the timer to expire before switching to the next CE level. In 4110 and 4120, the process starts, and the timer turns on. In 4130, the UE determines whether the RA procedure fails. The process begins with the UE initiating a random access (RA) procedure, receiving the timer value from the network node, and activating a timer (“Timer ON”). The UE then monitors the outcome of the RA procedure. The user equipment (UE) may be configured to receive the timer value from the network node at any point preceding, concurrent with, or subsequent to any of steps 4110 to 4130. These steps are well explained when discussing steps 3110 to 3140.

[0120] In 4140, the timer is discarded when the RA procedure is successful. If the RA procedure does not fail (i.e. , access is successful), the timer is discarded and the process ends in 4160. In 4150, the UE wait for the timer to expire and switch to the next CE level when the RA procedure fails. The process may then repeat, with the UE attempting access at the new CE level, until a predetermined condition is met (such as successful access, reaching the highest CE level, reaching the maximum switch times, low battery or another termination criterion). Then the process ends in 4160.

[0121] It should be noted that the flowchart is provided for illustrative purposes only and is not intended to limit the scope of the invention. For example, the step of switching to the next CE level is not restricted to a single switch or a strictly sequential approach. The UE may perform multiple CE level switches, including switching to any appropriate CE level based on network configuration, device status, or other criteria. The process may be repeated or adapted as needed to accommodate various operational scenarios.

[0122] FIG. 4b is a flowchart illustrating another exemplary process 4200 performed by the network node for coverage enhancement in the NTN according to some embodiments of the present disclosure. The method performed by the network node is also discussed in FIG. 3b. The process begins with the network node initiating the procedure (Start) in 4210. The network node then broadcasts a timer 202405302

[0123] 19 value to one or more user equipment (UE) devices in 4220. The broadcast of the timer value may be performed via system information signaling, such as a system information block (SIB) or RRC reconfiguration message, and is intended to provide the UEs with a predetermined timing parameter for use in access procedures, such as random access (RA) attempts and coverage enhancement (CE) level switching. Upon completion of the broadcast, the process ends in 4230. This mechanism enables consistent and coordinated timing control across multiple UEs, thereby supporting efficient and reliable network access in NTN environments.

[0124] FIG. 5a is a flowchart illustrating another exemplary process 5100 performed by the UE for coverage enhancement in the NTN according to some embodiments of the present disclosure. The timer is initiated when the UE starts RA procedure. The timer functions as follows:

[0125] 1. If the RA procedure is successful, the timer is discarded.

[0126] 2. Else, the UE waits for the timer to expire and re-try at the same CE level. If still RA fails, the UE switch to the next CE level.

[0127] The process begins in 5110, where the UE initiates the procedure (Start). In 5120, the UE activates a timer (Timer ON). In 5130, the UE determines whether the RA procedure has failed (RA failure?). The user equipment (UE) may be configured to receive the timer value from the network node at any point preceding, concurrent with, or subsequent to any of steps 5110 to 5130. These steps are well explained when discussing steps 3110 to 3140.

[0128] If the RA procedure is successful (No, F), the process proceeds to step 5140, where the timer is discarded (Timer is discarded), and then to step 5160, where the process ends (End).

[0129] If the RA procedure fails (Yes, T), the process proceeds to step 5150, where the UE waits for the timer to expire and then re-attempts the RA procedure at the same CE level (Wait for the timer to expire and re-try the same CE level). At step 5170, the UE determines again whether the second attempt of the RA procedure fails (RA failure?). If the second attempt is successful (No, F), the process proceeds to step 5160 (End). If the second attempt also fails (Yes, T), the process proceeds to step 5180, where the UE performs a CE level upgrade (CE level upgrade), after which the process may repeat as needed.

[0130] This process enables the UE to perform multiple access attempts at the same CE 202405302

[0131] 20 level before CE level switch. The UE gets an additional opportunity to use the same CE level, if RA is successful in the same CE level, the network congestion is reduced, and the UE will save energy.

[0132] It should be noted that the flowchart is provided for illustrative purposes only and is not intended to limit the scope of the invention. For example, the step of switching to the next CE level is not restricted to a single switch or a strictly sequential approach. The UE may perform multiple CE level switches, including switching to any appropriate CE level based on network configuration, device status, or other criteria. The process may be repeated or adapted as needed to accommodate various operational scenarios.

[0133] FIG. 5b is a flowchart illustrating another exemplary process 5200 performed by the network node for coverage enhancement in the NTN according to some embodiments of the present disclosure. The method performed by the network node is also discussed in FIG. 3b. The process begins with the network node initiating the procedure (Start) in 5210. The network node then broadcasts a timer value to one or more user equipment (UE) devices in 5220. The broadcast of the timer value may be performed via system information signaling, such as a system information block (SIB) or RRC reconfiguration message, and is intended to provide the UEs with a predetermined timing parameter for use in access procedures, such as random access (RA) attempts and coverage enhancement (CE) level switching. Upon completion of the broadcast, the process ends in 5230. This mechanism enables consistent and coordinated timing control across multiple UEs, thereby supporting efficient and reliable network access in NTN environments.

[0134] FIG. 6 is a block diagram illustrating an exemplary user equipment 600 according to some embodiments of the present disclosure. The UE includes a receiving module 610, a sending module 620, a timing module 630, a determining module 640 and a switch module 650. The receiving module 610 is configured to receive a predetermined timer value from a network node of a non-terrestrial network, NTN. The sending module 620 configured to send an access request to the network node to start a random access, RA, procedure. The timing module 630 is configured to initiate a timer of the UE when starting the RA procedure. The determining module 640 is configured to determine whether the RA procedure in a first coverage enhancement level is successful. The switching module 650 is 202405302

[0135] 21 configured to perform a coverage enhancement level switch in response to the failure of the RA procedure in the first coverage enhancement level after the timer exceeding the predetermined timer value. This configuration enables the UE to adaptively manage network access attempts and coverage enhancement procedures.

[0136] It should be understood that the above configuration is provided merely as an example. The user equipment (UE) may include additional modules, or certain modules described above may be omitted, so long as the UE is capable of achieving the same or substantially similar functionality. Various modifications to the disclosed embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be applied to other embodiments and applications without departing from the spirit and scope of the present disclosure. NTN loT, Uplink capacity enhancement is an ongoing Rel-19 WID. Therefore, the relaxed coverage enhancement for NTN networks is of high importance. It is highly relevant for 3GPP Release 19 onwards and of significant importance to NTN loT.

[0137] Non-terrestrial networks (NTN) typically exhibit wide beam coverage due to the substantial distance between the satellite and ground-based devices. The present disclosure introduces a multi-level coverage enhancement (CE) mechanism. By employing multiple CE levels, UEs experiencing weak coverage or located at greater distances from the satellite can incrementally enhance their access capability, for example, by increasing the number of repetitions or transmission power as the CE level increases. Additionally, timer-based control and dynamic CE level switching are utilized, enabling UEs to intelligently transition between CE levels in response to access feedback and timer expiration. This adaptive approach significantly improves the reliability of network access for devices across the entire coverage area, and is effective for UEs at the beam edge or in high- attenuation environments.

[0138] In non-terrestrial networks (NTN), a single footprint may cover thousands or even tens of thousands of user equipment (UE) devices simultaneously. This high device density results in extremely limited available resources per UE and creates a significant risk of access contention and network congestion, particularly during random access attempts. The present disclosure introduces timer-based control and distributed access mechanisms. Specifically, by employing timers, the timing 202405302

[0139] 22 of access attempts by different UEs can be controlled, thereby reducing the likelihood of simultaneous access collisions and mitigating random access channel (RACH) congestion. Furthermore, dynamic coverage enhancement (CE) level switching allows UEs to flexibly adjust their CE level based on network feedback, preventing excessive concentration of access attempts at a single CE level.

[0140] Non-terrestrial networks (NTN) are expected to support a vast number of low-cost, low-power Internet of Things (loT) devices, such as NB-loT, machine-type communication (MTC), and reduced capability (RedCap) terminals. These devices typically have limited processing and energy resources, which are unsuitable for complex access procedures or high-power operations. The present disclosure provides a low-complexity, adaptive access mechanism based on multi-level coverage enhancement (CE) and timer control. This approach enables low-cost, low-power devices to participate in network access procedures without the need for complex signaling or energy-intensive operations by setting a timer. Additionally, intelligent access control can allow each device to autonomously adjust its access strategy based on local status indicators, such as battery level, and network parameters, thereby prolonging device lifetime.

[0141] In non-terrestrial network (NTN) environments, spectrum resources are inherently limited. The present disclosure introduces mechanisms for optimizing resource utilization. By reducing unnecessary retries, distributing access attempts over time, and dynamically adjusting coverage enhancement (CE) levels, it improves the efficiency of wireless resource usage and minimizes resource waste. Although this approach does not directly increase the total available spectrum, it can enhance access capacity per unit spectrum by streamlining access procedures and optimizing resource allocation. Consequently, the system enables efficient access for a greater number of devices within limited spectrum resources, thereby alleviating spectrum bottlenecks and supporting scalable NTN deployments.

[0142] It should be understood that the foregoing description is provided for purposes of illustration and example, and is not intended to limit the scope of the present disclosure. Those skilled in the art will recognize that various modifications, substitutions, and alterations may be made without departing from the spirit and scope of the invention. References to “one embodiment,” “an embodiment,” or similar expressions are not intended to indicate that all such embodiments are 202405302

[0143] 23 mutually exclusive or that features described in connection with one embodiment cannot be combined with features of other embodiments. The particular features, structures, or characteristics described herein may be combined in any suitable manner in one or more embodiments. Furthermore, aspects of the present disclosure may be implemented in hardware, software, firmware, or any combination thereof, and may take the form of a process, apparatus, system, or computer program product embodied in one or more computer-readable media. The order of steps or use of numbers, letters, or other designations is not intended to limit the claimed subject matter except as expressly set forth in the claims. The appended claims are intended to cover all such modifications, equivalents, and variations that fall within the true spirit and scope of the invention, regardless of whether such features are described in a single embodiment, figure, or description herein.

Claims

1. 20240530224CLAIMS1 . A method performed by a user equipment, UE, for coverage enhancement for a non-terrestrial network, NTN, comprising: receiving a predetermined timer value from a network node of the NTN; sending an access request to the network node to start a random access, RA, procedure; initiating a timer of the UE when starting the RA procedure; determining whether the RA procedure in a first coverage enhancement level is successful; and performing a coverage enhancement level switch in response to the failure of the RA procedure in the first coverage enhancement level after the timer exceeding the predetermined timer value.

2. The method of claim 1 , further comprising: after determining whether the RA procedure in the first coverage enhancement level is successful, discarding the timer when the RA procedure in the first coverage enhancement level is successful; and establishing a connection between the UE and the network node.

3. The method of claims 1 or 2, the performing a coverage enhancement level switch in response to the failure of the RA procedure after the timer exceeding the predetermined timer value comprising: waiting for the timer to exceed the predetermined timer value; and switching to a second coverage enhancement level from the first coverage enhancement level.

4. The method of claims 1 or 2, the performing a coverage enhancement level switch in response to the failure of the RA procedure after the timer exceeding the predetermined timer value comprising: waiting for the timer to exceed the predetermined timer value when a first attempt of the RA procedure fails; performing a second attempt of the RA procedure after the timer exceeding the predetermined timer value;20240530225 determining whether the second attempt of the RA procedure is successful; and switching to a second coverage enhancement level from the first coverage enhancement level when the second attempt of the RA procedure is not successful.

5. The method of claim 4, further comprising: establishing a connection between the UE and the network node when the second attempt of the RA procedure is successful.

6. The method of claims 1 to 5, further comprising: receiving the predetermined timer value from the network node via a system information block, SIB, message and / or a radio resource control, RRC, reconfiguration message.

7. The method of claims 1 to 6, wherein the UE is any of a narrowband internet of things, NB-loT device, reduced capability, RedCap, device, and a machine-type communication, MTC, device compliant with NTN-loT standards.

8. The method of claims 1 to 7, wherein the step of preforming a coverage enhancement level switch is repetitive until a predetermined condition is met.

9. The method of claim 8, wherein the predetermined condition comprises any of:1 ) establishing a connection between the UE and the network node after the coverage enhancement level switch; and / or2) reaching to a highest coverage enhancement level in the NTN; and / or3) reaching to a predetermined number of the coverage enhancement level switch; and / or4) the UE reaching to a predetermined battery level.

10. A method, performed by a network node for coverage enhancement for a non-terrestrial network, NTN, comprising: broadcasting a predetermined timer value to one or more user equipment, UE, with a timer, wherein the one or more UE is configured to perform a coverage20240530226 enhancement level switch when a random access, RA, procedure fails after the timer exceeding the predetermined timer value; and establishing a connection with any of the one or more UE with a successful RA attempt.11 . The method of claim 10, the broadcasting a predetermined timer value to one or more user equipment, UE, with a timer comprising: broadcasting the predetermined timer value via a system information block, SIB, message and / or a radio resource control, RRC, reconfiguration message.

12. The method of claims 10 or 11 , wherein the NTN supports internet of things, loT, operation.

13. A user equipment, UE, comprising: a receiving module configured to receive a predetermined timer value from a network node of a non-terrestrial network, NTN; a sending module configured to send an access request to the network node to start a random access, RA, procedure; a timing module configured to initiate a timer of the UE when starting the RA procedure; a determining module configured to determine whether the RA procedure in a first coverage enhancement level is successful; and a switching module configured to perform a coverage enhancement level switch in response to the failure of the RA procedure in the first coverage enhancement level after the timer exceeding the predetermined timer value.

14. The user equipment of claim 13, wherein the UE is any of a narrowband internet of things, NB-loT device reduced capability, RedCap, device, and a machine-type communication, MTC, device compliant with NTN-loT standards.

15. A system for coverage enhancement for a non-terrestrial network, NTN, comprising: one or more user equipment, UE, configured to perform methods of any of claims 1 to 9; and20240530227 a network node configured to perform methods of any of claims 10 to 12.

Images