Contention resolution for non-terrestrial networks

Abstract

The embodiments of the present disclosure relate to a device, method, apparatus, and computer-readable storage medium for contention resolution for NTN. The method includes: determining whether an event occurs, the event including that a transmission of a message associated with a random access procedure is performed after a previous transmission of the message, or that an uplink grant associated with the message is received after a previous transmission; and determining a contention resolution failure based on the determination in the event when a timer for monitoring a downlink control channel between a second device and a first device expires. In this way, the problem of false declaration of contention resolution failure at the expiration of the contention resolution timer can be solved, and network blind scheduling for MSG3 retransmission can be realized.

Description

[Technical Field]

[0001] TECHNICAL FIELD Embodiments of the present disclosure relate generally to the field of telecommunications, and more particularly to contention resolution devices, methods, apparatus, and computer-readable storage media for non-terrestrial based networks (NTNs). [Background technology]

[0002] The 3rd Generation Partnership Project (3GPP) launched New Radio (NR) in the NTN WI in Release 17. To avoid wasting user equipment (UE) power consumption, the timer for physical downlink control channel (PDCCH) monitoring may not start immediately after the start of uplink (UL) transmission because the round trip time (RTT) may be very long in the NTN. Summary of the Invention

[0003] Generally, the exemplary embodiments of the present disclosure provide a conflict resolution solution for NTNs.

[0004] In a first aspect, a first device is provided, the first device comprising: at least one processor; and at least one memory including computer program code configured, using the at least one processor, to cause the first device to at least: determine whether an event has occurred, the event including that a transmission of a message associated with a random access procedure has been performed since a previous transmission of the message or that an uplink grant associated with the message has been received since the previous transmission; and determine a contention resolution failure based on the determination of the event when a timer for monitoring a downlink control channel between the second device and the first device expires.

[0005] In a second aspect, a method is provided, the method including: determining whether an event occurs, the event including a transmission of a message associated with a random access procedure being performed after a previous transmission of the message or a reception of an uplink grant associated with the message after a previous transmission; and determining a contention resolution failure based on the determination of the event when a timer for monitoring a downlink control channel between a second device and a first device expires.

[0006] In a third aspect, an apparatus is provided that includes means for determining whether an event has occurred, the event including a transmission of a message associated with a random access procedure being performed after a previous transmission of the message or a reception of an uplink grant associated with the message after a previous transmission; and means for determining a contention resolution failure based on the determination of the event when a timer for monitoring a downlink control channel between a second device and a first device expires.

[0007] In a fourth aspect, there is provided a computer readable medium having stored thereon a computer program which, when executed by at least one processor of a device, causes the device to perform a method according to the second aspect.

[0008] Other features and advantages of the disclosed embodiments will become apparent from the following description of specific embodiments, taken in conjunction with the accompanying drawings which illustrate, by way of example, the principles of the disclosed embodiments.

[0009] Embodiments of the present disclosure are presented by way of example, and their advantages will be explained in more detail below with reference to the accompanying drawings. [Brief explanation of the drawings]

[0010] [Figure 1]1 illustrates an example environment in which example embodiments of the present disclosure may be practiced. [Figure 2] 1 illustrates a time diagram illustrating the process of conflict resolution for an NTN, according to some example embodiments of the present disclosure. [Figure 3] 1 illustrates a flowchart of an example method of conflict resolution for NTNs according to some example embodiments of the present disclosure. [Figure 4] FIG. 1 shows a simplified block diagram of a device suitable for practicing exemplary embodiments of the present disclosure. [Figure 5] 1 illustrates a block diagram of an exemplary computer-readable medium according to some embodiments of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0011] Throughout the drawings, the same or similar reference numbers represent the same or similar elements.

[0012] The principles of the present disclosure will now be described with reference to several exemplary embodiments. It should be understood that these embodiments are set forth for illustrative purposes only, to assist those skilled in the art in understanding and practicing the present disclosure, but are not intended to imply any limitations on the scope of the present disclosure. The disclosure described herein can be implemented in various ways other than those described below.

[0013] In the following description and claims, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs, unless defined otherwise.

[0014] In this disclosure, references to "one embodiment," "embodiment," "exemplary embodiment," etc. indicate that the described embodiment may include a particular feature, structure, or characteristic, but do not require that every embodiment include that particular feature, structure, or characteristic. Moreover, such phrases do not necessarily refer to the same embodiment. Furthermore, when a particular feature, structure, or characteristic is described in connection with an exemplary embodiment, it is believed to be within the knowledge of one of ordinary skill in the art to affect such feature, structure, or characteristic with respect to other embodiments, whether or not explicitly stated.

[0015] It should be understood that terms such as "first" and "second" may be used herein to describe various elements. These elements should not be limited by these terms. These terms are used only to distinguish the function of the various elements. As used herein, the term "and / or" includes any and all combinations of one or more of the listed terms.

[0016] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting to example embodiments. As used herein, the singular forms "a," "an," and "the" are intended to include the plural forms unless the context clearly dictates otherwise. It will be further understood that as used herein, the terms "comprises," "comprising," "has," "having," "includes," and / or "including" specify the presence of stated features, elements, and / or components, etc., but do not exclude the presence or addition of one or more other features, elements, components, and / or combinations thereof.

[0017] As used in this application, the term "circuitry" may refer to one or more, or all, of the following: (a) a hardware-only circuit implementation (e.g., an implementation using only analog and / or digital circuitry); (b) any combination of hardware circuitry and software, such as (where applicable): (i) a combination of analog and / or digital hardware circuitry(s) and software / firmware; (ii) any portion of the hardware processor(s) using software (including digital signal processor(s), software, and memory(s)) that cooperate to cause a device, such as a mobile phone or server, to perform various functions; (c) Hardware circuit(s) and / or processor(s), such as microprocessor(s) or part of microprocessor(s), that require software (e.g., firmware) for operation, although software may be absent if not necessary for operation.

[0018] This definition of circuitry applies to all uses of the term in this application, including any claims. As a further example, the term circuitry, as used herein, encompasses implementations of a simple hardware circuit or processor (or processors), or portions of a hardware circuit or processor, as well as its (or their) accompanying software and / or firmware. The term circuitry also encompasses, for example, baseband or processor integrated circuits for mobile devices, or similar integrated circuits in servers, cellular network devices, or other computing or network devices, where applicable to certain claim elements.

[0019] As used herein, the term "communication network" refers to a network conforming to any suitable communication standard, such as a fifth-generation (5G) system, Long Term Evolution (LTE), LTE-Advanced (LTE-A), Wideband Code Division Multiple Access (WCDMA), High-Speed ​​Packet Access (HSPA), or Narrowband Internet of Things (NB-IoT). Furthermore, communications between terminal devices and network devices within a communication network may be performed according to any suitable generation of communication protocols, including, but not limited to, first-generation (1G), second-generation (2G), 2.5G, 2.75G, third-generation (3G), fourth-generation (4G), 4.5G, fifth-generation (5G) New Radio (NR) communication protocols, and / or any other protocols now known or later developed. Embodiments of the present disclosure may be applied to various communication systems. Given the rapid development in communications, there will, of course, be future communication technologies and systems capable of embodying the present disclosure. The scope of the present disclosure should not be considered as being limited to only the aforementioned systems.

[0020] As used herein, the term "network device" refers to a node in a communication network through which a terminal device accesses and receives services from the network. Depending on the terminology and technology applied, a network device may refer to a base station (BS) or an access point (AP), such as a Node B (NodeB or NB), evolved Node B (eNodeB or eNB), NR next-generation Node B (gNB), remote radio unit (RRU), radio header (RH), remote radio head (RRH), relay, low-power nodes such as femto and pico, etc. The RAN split architecture comprises a gNB-CU (centralized unit, hosting RRC, SDAP, and PDCP) that controls multiple gNB-DUs (distributed units, hosting RLC, MAC, and PHY). A relay node may correspond to the DU portion of an IAB node.

[0021] The term "terminal device" refers to any end device that may be capable of wireless communication. By way of example and not limitation, a terminal device may also be referred to as a communication device, user equipment (UE), subscriber station (SS), mobile subscriber station, mobile station (MS), or access terminal (AT). Terminal devices may include, but are not limited to, mobile phones, cell phones, smartphones, voice over IP (VoIP) phones, wireless local loop phones, tablets, wearable terminal devices, personal digital assistants (PDAs), portable computers, desktop computers, image capture terminal devices such as digital cameras, gaming terminal devices, music storage and playback devices, in-vehicle wireless terminal devices, wireless endpoints, mobile stations, laptop embedded equipment (LEE), laptop mounted equipment (LME), USB dongles, smart devices, wireless customer premises equipment (CPE), Internet of Things (IoT) devices, watches or other wearables, head-mounted displays (HMD), vehicles, drones, medical equipment and applications (e.g., remote surgery), industrial devices and applications (e.g., robots and / or other wireless devices operating in the context of industrial and / or automated processing chains), consumer electronics devices, devices operating on commercial and / or industrial wireless networks, etc. Terminal devices may also correspond to the mobile termination (MT) portion of an integrated access and backhaul (IAB) node (also known as a relay node). In the following description, the terms "terminal device", "communication device", "terminal", "user equipment" and "UE" may be used interchangeably.

[0022] While the functionality described herein may be performed in fixed and / or wireless network nodes in various exemplary embodiments, in other exemplary embodiments, the functionality may be implemented in a user equipment device (such as a cell phone, tablet computer, laptop computer, desktop computer, mobile IoT device, or fixed IoT device). This user equipment device may, for example, include corresponding functionality described in connection with the fixed and / or wireless network node(s), as appropriate. The user equipment device may be user equipment and / or a control device, such as a chipset or processor, configured to control the user equipment when installed in the user equipment. Examples of such functionality include a bootstrapping server function and / or a home subscriber server, which may be implemented in the user equipment device by providing the user equipment device with software configured to cause the user equipment device to execute in terms of these functions / nodes.

[0023] FIG. 1 illustrates an exemplary communication network 100 in which embodiments of the present disclosure can be implemented. As illustrated in FIG. 1, the communication network 100 may include a terminal device 110 (hereinafter also referred to as a UE 110 or a first device 110). The communication network 100 may further include a network device 120 (hereinafter also referred to as a gNB 120 or a second device 120). When the communication network 100 refers to an NTN, the network device 120 or a segment of the network device 120 can be considered to be located on a satellite. The network device 120 can manage a cell 102. The terminal device 110 and the network device 120 can communicate with each other within the coverage area of ​​the cell 102.

[0024] 1 is given for illustrative purposes without implying any limitation, and communication network 100 may include any suitable number of network devices and terminal devices.

[0025] It is currently agreed that the RTT between the UE and the gNB (UE-gNB RTT) is introduced to start some timers for the NTN, so that the UE only needs to start monitoring the PDCCH after the RTT.

[0026] Furthermore, it is agreed that the RA contention resolution timer is started in Message 3 (MSG3) transmitted over the NTN and that the RA contention resolution timer is restarted after every Hybrid Automatic Repeat Request (HARQ) retransmission at the first symbol after the end of the MSG3 transmission and the UE-gNB RTT estimated by the UE.

[0027] Due to the introduction of UE-gNB RTT, after a MSG3 retransmission, the contention resolution timer started by the previous MSG3 (re)transmission may expire before it is restarted after the RTT, which may lead to an unintended declaration of a contention resolution failure. In that case, the UE may perform a retry on the preamble transmission or may declare an RA failure if the maximum number of attempts is reached. In this situation, the UE may stop monitoring the PDCCH after the contention resolution timer expires, which may result in the loss of information transmitted by the gNB before an additional contention resolution timer starts.

[0028] The solution of the present disclosure proposes a mechanism for determining contention resolution failure. In this solution, the UE can determine whether an event has occurred, including whether a message associated with a random access procedure has been transmitted since the previous transmission of the message or whether an uplink grant associated with the message has been received since the previous transmission. The UE can then determine contention resolution failure based on the determination of the event when a timer for monitoring a downlink control channel between the second device and the first device expires. In this way, the problem of falsely declaring contention resolution failure upon expiration of the contention resolution timer can be solved, and network-blind scheduling of MSG3 retransmissions can be realized.

[0029] The principles and implementations of the present disclosure are described in detail below with reference to Figure 2, which shows a time diagram illustrating a process 200 of contention resolution for NTNs according to some example embodiments of the present disclosure. For illustrative purposes, process 200 is described with reference to Figure 1. Process 200 may include a UE 110 and a gNB 120.

[0030] Referring now to FIG. 2, at time T1, UE 110 may transmit MSG3 in a random access procedure. The transmission of MSG3 at T1 may be an initial transmission or a retransmission of MSG3. As mentioned above, since a UE-gNB RTT 210 is introduced, a contention resolution timer may be started after the UE-gNB RTT 210, i.e., at time T2. Within the duration 220 of the contention resolution timer, UE 110 may monitor the PDCCH for an UL grant from gNB 120. The UL grant may be associated with the MSG3 retransmission.

[0031] The contention resolution timer expires at time T5. Before the expiration of the contention resolution timer, UE 110 may determine whether an uplink grant has been received since the transmission of MSG3, i.e., since time T1, or whether a further transmission of MSG3 has been performed. In some example embodiments, the further transmission of MSG3 may be referred to as a retransmission of MSG3.

[0032] If an uplink grant is received after transmission of MSG3, for example at time T3, or if a further transmission of MSG3 is performed, for example at time T4, UE110 may determine that a contention resolution failure has not occurred when the timer expires, i.e., at time T5, and therefore UE110 may continue to monitor the PDCCH after the contention resolution timer expires.

[0033] In some example embodiments, if an uplink grant is received after the transmission of MSG3 or retransmission of MSG3 has been performed, the UE 110 may continue to monitor the PDCCH after the expiration of the contention resolution timer. In some example embodiments, the UE 110 may also monitor the PDCCH during the estimated UE-gNB RTT 230, even if the contention resolution timer is not yet running. In some other example embodiments, the UE 110 may monitor the PDCCH only after the UE-gNB RTT when the contention resolution timer is started or restarted.

[0034] In some example embodiments, a new timer may be introduced for potential blind scheduling that starts upon reception of a PDCCH for MSG3 retransmission or after an MSG3 retransmission. The UE 110 may also monitor the PDCCH for the duration of the new timer. Unlike the contention resolution timer, expiration of this new timer may not result in a declaration of a contention resolution failure. The UE 110 may stop monitoring the PDCCH upon expiration of this new timer. With the new timer, the contention resolution timer may be stopped upon reception of a PDCCH for an MSG3 retransmission or an MSG3 transmission without affecting the blind scheduling of the gNB 120.

[0035] It should be understood that the new timer may also be associated with other behaviors for PDCCH monitoring at UE 110 other than for MSG3 retransmission or reception of PDCCH after MSG3 retransmission.

[0036] In some exemplary embodiments, examples illustrating the possible impact of the mechanisms proposed in the specification may be given below. [Table 1]

[0037] In some example embodiments, another example may be given below that illustrates the possible impact of the mechanism proposed in the specification. [Table 2]

[0038] In some exemplary embodiments, further examples illustrating the possible impact of the mechanisms proposed in the specification may be given below. [Table 3]

[0039] Using the solution of the present disclosure, the problem of false declaration of contention resolution failure upon expiration of the contention resolution timer can be solved, and network-blind scheduling of MSG3 retransmissions can be realized.

[0040] 3 illustrates a flowchart of an example method 300 of conflict resolution for an NTN according to some example embodiments of the present disclosure. Method 300 may be implemented on first device 110 shown in FIG. 1. For illustrative purposes, method 300 will be described with reference to FIG. 1.

[0041] At 310, the first device determines whether an event has occurred, the event including whether a transmission of a message associated with the random access procedure has been performed since a previous transmission of the message or whether an uplink grant associated with the message has been received since a previous transmission.

[0042] At 320, the first device determines a contention resolution failure based on determining in the event that a timer for monitoring a downlink control channel between the second device and the first device expires.

[0043] In some example embodiments, if the first device determines that an event has occurred, the first device may determine that a conflict resolution failure has not occurred when the timer expires.

[0044] In some example embodiments, the first device may continue to monitor the downlink control channel after the timer expires.

[0045] In some example embodiments, if the first device determines that the message has been retransmitted, the first device may continue to monitor the downlink control channel for the round-trip time between the first device and the second device before an additional timer for monitoring the downlink control channel starts.

[0046] In some example embodiments, the first device may continue to monitor the downlink control channel based on an additional timer, the additional timer being associated with one of receiving an uplink grant or retransmitting a message.

[0047] In some example embodiments, the first device, while expiring the timer, may start an additional timer associated with one of receiving an uplink grant or retransmitting the message, and continue to monitor the downlink control channel for the duration of the additional timer.

[0048] In some example embodiments, the message is message 3 in a random access procedure.

[0049] In some example embodiments, the first device comprises a terminal device and the second device comprises a network device.

[0050] In some example embodiments, an apparatus capable of performing method 300 (e.g., implemented in UE 110) may comprise means for performing each step of method 300. The means may be implemented in any suitable manner. For example, the means may be implemented in circuitry or software modules.

[0051] In some example embodiments, the apparatus comprises: means for determining whether an event has occurred, the event including whether a transmission of a message associated with a random access procedure has been performed since a previous transmission of the message or whether an uplink grant associated with the message has been received since a previous transmission; and means for determining a contention resolution failure based on the determination in the event when a timer for monitoring a downlink control channel between the second device and the first device expires.

[0052] 4 is a simplified block diagram of a device 400 suitable for implementing embodiments of the present disclosure. The device 400 may be provided to implement a communications device, such as the UE 110 shown in FIG. 1. As shown, the device 400 includes one or more processors 410, one or more memories 440 coupled to the processors 410, and a communications module 440 coupled to the processors 410.

[0053] The communications module 440 is for bidirectional communication. The communications module 440 has one or more communications interfaces to facilitate communication with one or more other modules or devices. The communications interfaces may represent any interface necessary for communication with other network elements. In some example embodiments, the communications module 440 may include at least one antenna.

[0054] Processor 410 may be of any type suitable for a local technology network and may include, by way of non-limiting example, one or more of a general purpose computer, a special purpose computer, a microprocessor, a digital reference signal processor (DSP), and a processor based on a multi-core processor architecture. Device 400 may have multiple processors, such as application specific integrated circuit chips time-slaved to a clock that synchronizes the main processor.

[0055] The memory 420 may include one or more non-volatile memories and one or more volatile memories. Examples of non-volatile memory include, but are not limited to, read-only memory (ROM) 424, electrically programmable read-only memory (EPROM), flash memory, hard disks, compact disks (CDs), digital video disks (DVDs), and other magnetic and / or optical storage devices. Examples of volatile memory include, but are not limited to, random access memory (RAM) 422 and other volatile memory that does not persist while power is off.

[0056] The computer program 430 includes computer-executable instructions that are executed by the associated processor 410. The program 430 may be stored in ROM 420. The processor 410 can load the program 430 into RAM 420 to perform any appropriate actions and processes.

[0057] The embodiments of the present disclosure may be implemented by a program 430 such that the device 400 can execute any of the processes of the present disclosure described with reference to Figures 2 and 3. The embodiments of the present disclosure may also be implemented by hardware or a combination of software and hardware.

[0058] In some embodiments, the program 430 may be tangibly contained in a computer-readable medium that may be included in the device 400 (such as the memory 420) or in other storage accessible by the device 400. The device 400 may load the program 430 from the computer-readable medium into RAM 422 for execution. The computer-readable medium may include any type of tangible non-volatile storage, such as a ROM, an EPROM, a flash memory, a hard disk, a CD, a DVD, etc. Figure 5 shows an example of a computer-readable medium 500 in the form of a CD or DVD. The computer-readable medium has the program 430 stored thereon.

[0059] In general, various embodiments of the present disclosure may be implemented in hardware or special purpose circuits, software, logic, or any combination thereof. Some aspects may be implemented in hardware, while other aspects may be implemented in firmware or software that may be executed by a controller, microprocessor, or other computing device. While various aspects of embodiments of the present disclosure are shown and described as block diagrams, flowcharts, or using some other graphical representations, it should be understood that the blocks, devices, systems, techniques, or methods described herein may be implemented in, by way of non-limiting example, hardware, software, firmware, special purpose circuits or logic, general purpose hardware or controller, or other computing device, or some combination thereof.

[0060] The present disclosure also provides at least one computer program product tangibly stored on a non-transitory computer-readable storage medium. The computer program product includes computer-executable instructions, such as those included in program modules and executed by a target real or virtual processor device, for performing the method 300 described above with reference to FIG. 3. Generally, program modules include routines, programs, libraries, objects, classes, components, data structures, etc. that perform particular tasks or implement particular abstract data types. The functionality of the program modules may be combined or split among program modules as desired in various embodiments. The machine-executable instructions for the program modules may be executed in a local device or in a distributed device. In a distributed device, the program modules may be located in both local and remote storage media.

[0061] Program code for carrying out the methods of the present disclosure may be written in any combination of one or more programming languages. These program codes may be provided to a processor or controller of a general-purpose computer, a special-purpose computer, or other programmable data processing apparatus such that, when executed by the processor or controller, the functions / acts specified in the flowcharts and / or block diagrams are performed. The program code may run entirely on the machine, partly on the machine as a stand-alone software package, partly on the machine and partly on a remote machine, or entirely on a remote machine or server.

[0062] In the context of the present disclosure, computer program code or associated data may be carried by any suitable carrier to enable a device, device, or processor to perform the various processes and operations described above. Examples of carriers include reference signals, computer-readable media, etc.

[0063] The computer-readable medium may be a computer-readable reference signal medium or a computer-readable storage medium. The computer-readable medium may include, but is not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, device, or device, or any suitable combination thereof. More specific examples of the computer-readable storage medium may include an electrical connection having one or more wires, a portable computer diskette, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber, a portable compact disc read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination thereof.

[0064] Furthermore, although operations are shown in a particular order, this should not be understood as requiring such operations to be performed in the particular order shown, or sequentially, or that all of the operations shown be performed, to achieve desirable results. Multitasking and parallel processing may be advantageous in certain situations. Similarly, although details of several specific implementations are included in the above discussion, these should not be construed as limitations on the scope of the disclosure, but rather as descriptions of features that may be specific to particular embodiments. Certain features that are described in the context of separate embodiments can also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment may also be implemented in multiple embodiments separately or in any suitable subcombination.

[0065] Although the present disclosure has been described in language specific to structural features and / or methodological acts, it is to be understood that the present disclosure, as defined by the appended claims, is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims.

Claims

1. a first device, at least one processor; at least one memory containing computer program code; Equipped with The at least one memory and the computer program code are used by the at least one processor to provide the first device with at least: determining whether a physical downlink control channel (PDCCH) between a second device and the first device is received after starting a random access contention resolution timer for monitoring the PDCCH, the PDCCH being addressed to a temporary cell radio network temporary identifier and indicating an uplink grant for a retransmission of a message, the message being Message 3 of a random access procedure; when the random access contention resolution timer expires, discarding the temporary cell radio network temporary identifier and deeming contention resolution unsuccessful in accordance with a determination that the uplink grant for the retransmission of the message 3 was not received after the start of the random access contention resolution timer; The first device is configured to cause

2. The at least one memory and the computer program code are used by the at least one processor to determining that a contention resolution failure has not occurred when the random access contention resolution timer expires in accordance with a determination that the uplink grant for the retransmission of the message 3 was received after the start of the random access contention resolution timer. The first device of claim 1 configured to:

3. The at least one memory and the computer program code are used by the at least one processor to Continue monitoring the PDCCH after the expiration of the random access contention resolution timer. The first device of claim 2 configured to:

4. The at least one memory and the computer program code are used by the at least one processor to while expiring the random access contention resolution timer, starting a further timer associated with receiving the uplink grant; continuing to monitor the PDCCH for the duration of the further timer; The first device of claim 1 configured to:

5. The first device of claim 1 , wherein the first device comprises a terminal device and the second device comprises a network device.

6. 6. The first device of claim 1, wherein the random access contention resolution timer is started at the first symbol after adding a round trip time (RTT) between the first device and the second device at the end of the message 3 transmission.

7. The first device according to any of claims 1 to 6, wherein the message 3 is transmitted over a non-terrestrial network (NTN).

8. 1. A method comprising: determining, by the first device, whether a physical downlink control channel (PDCCH) between a second device and a first device is received after starting a random access contention resolution timer for monitoring the PDCCH, the PDCCH being addressed to a temporary cell radio network temporary identifier indicating an uplink grant for a retransmission of a message, the message being Message 3 of a random access procedure; when the random access contention resolution timer expires, discarding the temporary cell radio network temporary identifier in accordance with a determination that the uplink grant for the retransmission of the message 3 was not received after the start of the random access contention resolution timer, and deeming contention resolution unsuccessful. The method comprising:

9. The method comprises: determining that a contention resolution failure has not occurred when the random access contention resolution timer expires in accordance with determining that the uplink grant for the retransmission of the message 3 was received after the start of the random access contention resolution timer. The method of claim 8, comprising:

10. The method comprises: continuing to monitor the PDCCH after the expiration of the random access contention resolution timer.

10. The method of claim 9, comprising:

11. The method comprises: while expiring the random access contention resolution timer, starting a further timer associated with receiving the uplink grant; continuing to monitor the PDCCH for the duration of the further timer; The method of claim 8, comprising:

12. The method of claim 8 , wherein the first device comprises a terminal device and the second device comprises a network device.

13. 13. The method of claim 8, wherein the random access contention resolution timer is started on the first symbol after adding a round trip time (RTT) between the first device and the second device at the end of the message 3 transmission.

14. The method according to any of claims 8 to 13, wherein the message 3 is transmitted over a non-terrestrial network (NTN).

15. 1. An apparatus comprising: means for determining, by the first device, whether a physical downlink control channel (PDCCH) between a second device and a first device is received after starting a random access contention resolution timer for monitoring the PDCCH, the PDCCH being addressed to a temporary cell radio network temporary identifier indicating an uplink grant for a retransmission of a message, the message being Message 3 of a random access procedure; when the random access contention resolution timer expires, discarding the temporary cell radio network temporary identifier in accordance with a determination that the uplink grant for the retransmission of the message 3 was not received after the start of the random access contention resolution timer, and deeming contention resolution unsuccessful. The device comprising:

16. A non-transitory computer readable medium comprising program instructions for causing an apparatus to perform at least the method according to any one of claims 8 to 14.

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