GB2621443A

GB2621443A - Enhancements for UE - satellite access

Info

Publication number: GB2621443A
Application number: GB2308581.4A
Authority: GB
Inventors: Khirallah Chadi; Watfa Mahmoud; Kumar Lalith
Original assignee: Samsung Electronics Co Ltd
Current assignee: Samsung Electronics Co Ltd
Priority date: 2022-08-08
Filing date: 2023-06-08
Publication date: 2024-02-14
Also published as: GB202308581D0

Abstract

A method of a radio access network (RAN) entity in a network, wherein a user equipment (UE) uses at least one satellite to access the network (i.e. a non-terrestrial network (NTN)), and wherein satellite coverage is discontinuous, the method comprising: identifying loss of satellite coverage for the UE; in response to identifying loss of satellite coverage and identifying insufficient time to complete a procedure, releasing the UE. The procedure may be a NAS procedure or RRC procedure and releasing the UE may comprise context release or RRC release. Insufficient time to complete a procedure may be determined based on satellite flyover time. A further method of a RAN entity in a network, wherein a UE uses at least one satellite to access the network, the method comprising: transmitting information to the UE, wherein the information enables the UE to determine at least one of; loss of satellite coverage, start of discontinuous coverage, or remaining flyover time, and to determine insufficient time to complete a procedure. A further method of a UE in a network wherein the UE uses at least one satellite to access the network, and wherein satellite coverage is discontinuous, the method comprising identifying loss of satellite coverage and determining insufficient time to complete a procedure.

Description

Enhancements for UE -Satellite Access

BACKGROUND

Field

Certain examples of the present disclosure provide various techniques relating to enhancements for UE -satellite access for example within 3rd Generation Partnership Project (3GPP) 5th Generation (5G) communication networks using such access.

Description of the Related Art

The Yd Generation Partnership Project (3GPP) is developing solutions for the use of satellite access for connecting UEs, such as loT devices, to core networks, such as the evolved packet core (EPC).

One of the related aspects of this satellite use is discontinuous coverage (DC), in which a satellite's coverage is not always available for a UE, and hence it's satellite access is discontinuous. The lack of availability of satellite coverage for a UE is due to the movement of the satellite around the planet. When the satellite is near the UE, the UE will have coverage from the satellite. When the satellite is moving around the planet, a certain time being required for a full circle to be made, the UE will not have coverage from the satellite. When the satellite is again near the UE, the UE will have coverage from the satellite. In the presence of the satellite, and hence coverage, the concept of fly-over time is discussed which is basically the duration of time for which coverage is available to the UE. As an example, a satellite may take hours (10hrs, as an example) to go around the Earth at a certain orbit or distance. A satellite may have a fly-over time for a UE on Earth of only minutes (2mins, as an example) and the UE on Earth will only detect coverage every 10hrs.

Additionally, when using satellite communication, a UE will not be able to send any message if it does not have the satellite location or position. The time needed to do so is referred to as Time To First Fix (TTFF). The duration of TTFF depends on the state of the UE receive function, which may be one of three states: cold, warm, or hot. The 3GPP RAN2 working group has assumed certain example values, such that from a cold state, the global navigation satellite system (GNSS) fix can take up to 100s, from a warm state, 50s and from hot start, 2s.

It should be noted that when a UE is using satellite access, the network access server (NAS) timers that guard the NAS procedures are extended, so as to give enough time for lower layer transmissions of the UE to succeed and for a response to arrive at the UE from a message recipient. For example, the timer T3517 (in Ni mode) for the service request procedure (for which, for example, the UE sends the Service Request message) is 15s when the UE is not using satellite access. However, when satellite access is used, this timer is set to 27s. This is because the lower layer transmissions in satellite access are expected to require more time to transmit a message. Setting the timer to 15s would lead to an early failure of the NAS procedure, even if the response message may well be received a few seconds after the 15s time mark. To avoid this, the NAS timers have been extended in TS 24.301 and IS 24.501.

The NAS timers may have different names in Si mode compared to Ni mode and may also have different values depending on whether the UE is using narrow band or wide band, etc. The following problems have been identified. Consider the following example: assume a satellite's flyover time starts at Ti and it is expected to last until Ti + 60s. At time T2, which is, say, equal to Ti + 50s, i.e. 50s into the flyover time, the satellite is expected to provide coverage for an additional 10s. A UE in idle mode may have data or signalling to send at T2. This means that the UE only has 10s left to complete the service request procedure, for which the NAS timer is to be set at 27s. The remaining 10s of flyover time would likely be insufficient for the completion of the NAS procedure. The NAS procedure will therefore almost be guaranteed to be unsuccessful due to lack of enough coverage time. A failed NAS procedure means that the UE would have wasted power in the NAS procedure. Note that, as mentioned earlier, the NAS timers may be different in Si mode and also the timer values may be different and can be longer than the example used here.

In RAN#96 meeting, 3GPP approved a new WI for loT (Internet of Things) NTN (non-terrestrial network) enhancements [1]. The following are some of the main objectives in this WI: Specify the following loT NTN specific enhancements not covered by NR NTN Solutions WI agreements, according to Section 8 in TR 36.763: Architecture: Support for EPC Mobility and Tracking Area: Support of legacy (Re1-16) cell selection/reselection mechanisms without major enhancements. Minor adjustments to existing mobility mechanisms, such as a new parameter values, change to timing etc. can be considered to adapt functionality to NTN.

Support of legacy (Re1-16) Handover and RLF/reestablishment mechanisms without major enhancements. For eMTC, Pei-16 LTE CHO procedure can be considered without major enhancements. Minor adjustments to existing mobility mechanisms, such as a new parameter values, change to timing etc. can be considered to adapt functionality to NTN.

Others: Support of discontinuous coverage without excessive UE power consumption and without excessive failures /recovery actions. Minor enhancements to the existing power saving mechanisms e.g. DRX, PSM, eDRX, relaxed monitoring, and (G)WUS can be considered, and if found needed, specified, to support discontinuous coverage; In discontinuous coverage (DC) scenarios, the satellite's coverage may only be visible to the UE during so called satellite's fly-over time. Example of flyover times and coverage times can be found in [2].

Consequently, it is expected that signalling between the UE and the network maybe impacted, due to in insufficient flyover time to complete a given procedure in discontinuous coverage 20 scenario.

Moreover, 3GPP is also working on the specification of the idle mode procedures for the UE when the scenario of discontinuous coverage (DC) is used in the network. According to TS 23.401, the following requirement is mentioned in relation to the deactivation of the access stratum due to DC: For UE using a RAN that provides discontinuous coverage (e.g. for satellite access with discontinuous coverage), if the UE knows how the E-UTRAN coverage varies with time based on information defined in TS 36.331 [37] (e.g. from the ephemeris data of a satellite access system that the UE is using) then the UE may deactivate its Access Stratum functions in order to optimise power consumption until coverage returns.

Details are specified in TS 36.304 [34] and TS 24.301 [46].

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

SUMMARY

It is an aim of certain examples of the present disclosure to address, solve and/or mitigate, at least partly, at least one of the problems and/or disadvantages associated with the related art, for example at least one of the problems and/or disadvantages described herein. It is an aim of certain examples of the present disclosure to provide at least one advantage over the related art, for example at least one of the advantages described herein.

The present invention is defined in the independent claims. Advantageous features are defined in the dependent claims. Embodiments or examples disclosed in the description and/or figures falling outside the scope of the claims are to be understood as examples useful for understanding the present invention.

Other aspects, advantages, and salient features of the invention will become apparent to those skilled in the art from the following detailed description taken in conjunction with the accompanying drawings.

According to one aspect of the present disclosure there is provided for a UE in a communications network using a satellite to access the network, a method comprising verifying if a communication process between the UE and the satellite can be completed before expiration of a flyover time of the satellite or can not be completed before expiration of a flyover time of the satellite.

The communication process may be a process initiated by the UE. The communication process may be a process initiated by the UE on receipt of a message from the network.

The communication process may comprise a NAS communication procedure. The communication process may comprise initiation of a NAS procedure. The communication process may comprise completion of a NAS procedure.

Completion of the communications process before expiration of the flyover time of the satellite may comprise the UE transmitting a message to the network. Completion of the communications process before expiration of the flyover time of the satellite may further comprise the UE receiving an expected response message from the network.

Verifying if the communication process can or can not be completed before expiration of a flyover time of the satellite may use at least one time value. The time value may comprise a time period before a NAS timer expires. The time value may comprise a remaining time period between a current time and an expiration time of the flyover time. The time value may comprise a time period for completion of the communication process.

Verifying that the communication process can be completed before expiration of a flyover time of the satellite may comprise determining that the time value comprising the remaining time period is greater than the time value comprising the time period for completion of the communication process.

The time value may comprise a minimum time period. Verifying that the communication process can be completed before expiration of a flyover time of the satellite may comprise determining that the time value comprising the remaining time period is greater than or equal to the time value comprising the minimum time period.

The minimum time period may be received by the UE from the network. The minimum time period may be part of the UE subscription information The minimum time period may be determined by the UE.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a block diagram of an exemplary UE that may be used in examples of the present

disclosure;

Figure 2 is a flow chart illustrating the method of the invention when the communication process comprises sending a NAS message; Figure 3a (Alt-1) illustrates an example of UE behaviour depending on remaining satellite fly-30 overtime; Figure 3b (Alt-2) illustrates an example of UE behaviour depending on remaining satellite flyover time; Figure 3c (Alt-3) illustrates an example of UE behaviour depending on remaining satellite flyover time; Figure 4 shows an example NG-RAN behaviour based on some of the proposals herein; Figure 5 shows an example of the UE sending an indication (e.g. insufficientTimeToCompleteProcIE) to the network (e.g. NG-RAN) for its preference to leave an RRC mode/state. Figure 3 illustrates an example of providing UE preference to move out of RRC-CONNECTED with the indication of insufficientTimeToCompleteProc 1E, and Figure 6 shows an example of NG-RAN including a new cause value = insufficientTimeToCompleteProc" in the UE Context Release Request procedure to request the AMF to release UE context. Figure 4 illustrates an example of including a new cause value "insufficientTimeToCompleteProc " in UE CONTEXT RELEASE REQUEST message (i.e. moving UE out of RRC_CONNECTED state).

DETAILED DESCRIPTION

The following description of examples of the present disclosure, with reference to the accompanying drawings, is provided to assist in a comprehensive understanding of the present invention, as defined by the claims. The description includes various specific details to assist in that understanding but these are to be regarded as merely exemplary. Accordingly, those of ordinary skill in the art will recognize that various changes and modifications of the examples described herein can be made.

The following examples are applicable to, and use terminology associated with, 3GPP 53. However, the skilled person will appreciate that the techniques disclosed herein are not limited to these examples or to 3GPP 5G, and may be applied in any suitable system or standard, for example one or more existing and/or future generation wireless communication systems or standards. The skilled person will appreciate that the techniques disclosed herein may be applied in any existing or future releases of 3GPP 53 NR or any other relevant standard.

For example, the functionality of the various network entities and other features disclosed herein may be applied to corresponding or equivalent entities or features in other communication systems or standards. Corresponding or equivalent entities or features may be regarded as entities or features that perform the same or similar role, function, operation or purpose within the network.

The skilled person will appreciate that the present invention is not limited to the specific examples disclosed herein. For example: * The techniques disclosed herein are not limited to 3GPP 5G.

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

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

* One or more further elements, entities and/or messages may be added to the examples disclosed herein.

* One or more non-essential elements, entities and/or messages may be omitted in certain examples.

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

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

* Information carried by a particular message in one example may be carried by two or more separate messages in an alternative example.

* Information carried by two or more separate messages in one example may be carried by a single message in an alternative example.

* The order in which operations are performed may be modified, if possible, in alternative examples.

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

For a UE in a communications network using a satellite to access the network, a method of the present disclosure comprises verifying if a communication process between the UE and the satellite can be completed before expiration of a flyover time of the satellite or can not be completed before expiration of a flyover time of the satellite.

The above is a general UE behaviour of the present disclosure. The following describes details that can be used to achieve the above aspect. These details are examples only and they may be used in any combination or order.

The method at least alleviates the problem of wasted power and unnecessary signalling overhead between the UE and the network, as a result of incomplete communication procedures.

Figure 1 is a block diagram of an exemplary UE that may be used in examples of the present disclosure. The skilled person will appreciate that the network entity illustrated in Figure 1 may be implemented, for example, as a network element on a dedicated hardware, as a software instance running on a dedicated hardware, or as a virtualised function instantiated on an appropriate platform, e.g. on a cloud infrastructure.

The UE 200 comprises a processor (or controller) 201, a transmitter 203 and a receiver 205.

The receiver 205 is configured for receiving one or more messages from one or more other entities of the communications network and the satellite. The transmitter 203 is configured for transmitting one or more messages to one or more other entities of the communications network and the satellite. The processor 201 is configured for performing operations as described below.

The flyover time of the satellite may be a time period within which the satellite provides coverage for the UE. The expiration of the flyover time of the satellite may be a time at which a discontinuous coverage (DC) event occurs.

The method may comprise the UE verifying that the communication process can be completed and then initiating the communication process.

The method may comprise the UE verifying that the communication process can not be completed and then determining not to initiate the communication process. This may be the case even if satellite access/coverage is still available, or even if the remaining satellite flyover time is not zero, or even if a next satellite DC event has not yet started.

The method may comprise the UE verifying that the communication process cannot be completed and any of keeping UE access stratum functions deactivated, deactivating UE access stratum function, remaining in idle mode, entering idle mode optionally by the UE locally releasing its NAS signalling connection, staying in current mode, remaining in power saving mode, activating power saving mode, starting a timer to guard the release of the NAS signalling connection by the network (e.g. starting T3540 in 5G or the equivalent in LTE e.g. T3440) and after the expiry of which the UE may then enter idle mode.

The communication process may be a process initiated by the UE. The communication process may be a process initiated by the UE on receipt of a message from the network. The message from the network may comprise a page. The UE may receive a page and verify whether a response to the page can be completed before expiration of a flyover time of the satellite or cannot be completed before expiration of a flyover time of the satellite.

The communication process may comprise a NAS procedure. The communication process may comprise initiation of a NAS procedure. The communication process may comprise completion of a NAS procedure. The NAS procedure may be a NAS message. The NAS message may be a NAS request. The NAS message may be NAS signalling. The NAS signalling may be for any of sending data, requesting resources for data. The communication procedure may be a RRC procedure. The RRC procedure may be a RRC message. The RRC procedure may be RRC signalling.

Completion of the communication process before expiration of the flyover time of the satellite may comprise the UE transmitting a message to the network. Completion of the communication process before expiration of the flyover time of the satellite may further comprise the UE receiving an expected response message from the network.

Completion of a communication process comprising a NAS procedure before expiration of the flyover time of the satellite may comprise transmission of a NAS message to the network.

Completion of a communication process comprising a NAS procedure before expiration of the flyover time of the satellite may further comprise receiving an expected response message from the network. The expected response message may be a NAS response message.

In one embodiment, the NAS procedure may be a Registration Request message and the expected response message may be a NAS response message comprising any of a Registration Accept, a Registration Reject. In another embodiment, in LTE (i.e. Si mode), the NAS procedure may comprise a Service Request message and the expected response message may be any NAS message, such as any of a Security Mode Command message, indication from UE lower layers that bearers have been established, or any other method that is known to be an indication of the success of the NAS procedure in question.

The method may comprise verifying if the communication process can or can not be completed before expiration of a flyover time of the satellite by using at least one time value.

The time value may comprise a time period before a NAS timer expires.

The time value may comprise a remaining time period, Trem, between a current time and an expiration time of the flyover time. This is basically the time period in which the satellite coverage remains available and hence the UE can (at least in theory) initiate the communication process. The method may comprise determination of the expiration time of the flyover time. This may be equivalent to determination of a start time of a next DC event.

The time value may comprise a time period for completion of the communication process.

The method may comprise verifying that the communication process can be completed before expiration of a flyover time of the satellite by determining that the time value comprising the remaining time period is greater than the time value comprising the time period for completion of the communication process.

The time period for completion of the communication process may comprise a time period between a start of a communication procedure of the communication process and an end of the communication procedure. The communication procedure may comprise transmission of a message by the UE. The time period for completion of the communication process may further comprise a time period for the UE to be in a state which permits start of a communication procedure of the communication process.

The time period for the UE to be in a state which permits start of a communication procedure of the communication process may be zero. This may occur if the UE is already in a state which permits the UE to start the communication procedure.

The method may comprise determination of whether the UE is in a state which permits start of the communication procedure. This may comprise any of: * the UE's lower layers are such that they are ready to start the communication procedure without needing any GNSS fix time, or without needing Time To First Fix (TTFF), * the UE is in 5GMM-CONNECTED mode (or EMM-CONNECTED mode), or 5GMM-CONNECTED mode with RRC inactive indication, * the UE is in 5GMM-IDLE mode (or EMM-IDLE mode), or in 5GMM-IDLE mode with suspend indication (EMM-IDLE mode with suspend indication), * the UE is in RRC-CONNECTED state or RRC-INACTIVE state, * the UE is in RRC-IDLE state, Any combinations of the above may apply, however what is important is that the UE's lower layers do not need additional time to be ready to start the communication procedure.

The time period for the UE to be in a state which permits start of a communication procedure of the communication process may be non-zero. The method may comprise determining the non-zero time period for the UE to be in a state which permits start of the communication procedure.

The UE may not be in a state which permits start of the communication procedure as the UE needs time for the lower layers thereof to start the communication procedure. For example, the UE may need a non-zero time period to start the communication procedure due to GNSS fix time (or Time To First Fix) due to the UE being, e.g. in cold state, warm state, hot state, etc. The UE should consider the time required by the lower layers of the UE to be in a certain state which permits the communication procedure, which may comprise transmission of a message. For example, the UE may consider the time required to enter a RRC-CONNECTED state from any state that the UE may currently be in e.g. a RRC-IDLE state. As such, when determining if there is sufficient time to complete the communication process, e.g. sending a NAS message or initiating a NAS procedure, the UE may consider at least one aspect such as those listed herein e.g. time to fix, time to be in a RRC-CONNECTED state, remaining flyover time, etc. The time value may comprise a minimum time period, T_min.

The method may comprise verifying that the communication process can be completed before expiration of a flyover time of the satellite by determining that the time value comprising the remaining time period is greater than the time value comprising the minimum time period. The method may comprise verifying that the communication process can be completed before expiration of a flyover time of the satellite by determining that the time value comprising the remaining time period is equal to the time value comprising the minimum time period.

When this is the case, the UE can initiate the communication process.

The method may comprise verifying that the communication process can not be completed before expiration of a flyover time of the satellite by determining that the time value comprising the remaining time period is less than the time value comprising the minimum time period.

When this is the case, the UE will not initiate the communication process.

The above proposals may apply to a UE in any NAS mode e.g. idle mode, connected mode, idle mode with suspend indication, or connected mode with RRC inactive indication (which only applies to Ni mode i.e. 5GS).

It should be noted that: * a NAS idle mode may refer to: EMM-IDLE mode (in Si mode), or 53MM-IDLE mode (in Ni mode), * a NAS idle mode with suspend indication may refer to: EMM-IDLE mode with suspend indication, or 5M M-IDLE mode with suspend indication, * a NAS connected mode may refer to: EMM-CONNECTED mode, or 5GMMCONNECTED mode * a NAS connected mode with RRC inactive indication may refer to: 53MM-CONNECTED mode with RRC inactive indication.

The above proposals also apply to a UE in Si mode (i.e. EPS) or to a UE in Ni mode (i.e. 53S). For the proposals herein, the UE may be in state of the REGISTERED or DEREGISTERED state in either Si mode or Ni mode. The UE may also be in any substate 15 of the REGISTERED or DEREGISTERED state (in either Ni mode or S1 mode).

Referring to Figure 2, a flow chart illustrates the above proposals when the communication process includes sending a NAS message.

When the time value comprising the minimum time period, T_min, is used in the method, the UE should ensure that the minimum time period is known and/or well determined for the purpose of deciding if the communication process can be completed or not.

The minimum time period may comprise a value of a NAS timer which is associated with transmission of a communication procedure of the communication process comprising a NAS message, or to a fraction of the value of the NAS timer which is associated with the transmission of the NAS message. The minimum time period may be a predetermined minimum time period. Optionally the predetermined minimum time period may be a time period associated with a mobility management message. Optionally the predetermined minimum time period may be a time period associated with a session management message.

The minimum time may also mean that the UE should also consider the time required by the lower layers to be in a certain state which permits the transmission of a message. For example, the UE may consider the time required to enter RRC-CONNECTED state from any state that the UE may currently be in e.g. RRC-IDLE state. As such, when determining if there is sufficient time to send a NAS message or initiate a NAS procedure, the UE may consider at least one aspect such as those listed herein e.g. time to fix, time to be in RRC-CONNECTED state, remaining flyover time, etc. The minimum time period may be received by the UE from the network. The minimum time 5 period may be received by the UE from the network in a NAS message. The NAS message may comprise any of a Registration Accept, an Attach Accept, a Configuration Update Command, a Service Accept, a PDU Session Establishment Accept message, any similar message that is used in EPS. The NAS message may be any new or existing message. The NAS message may be either a NAS mobility management message or a NAS session 10 management message or both. The minimum time period may be received by the UE from the network in any of a container, a policy container, a part of steering information, a part of roaming information.

In another possibility, the minimum time period received by the UE from the network may be associated with any of a NAS mobility management message, NAS mobility management procedure, a NAS session management message or procedure. It is also possible the minimum time period received by the UE from the network may be associated with a particular message type such as a Registration Request, a Tracking Area Update Request, a Service Request.

The network may determine the minimum time period based on implementation details, and/or based on knowledge of the discontinuous coverage time period, and/or based on consideration of a GNSS fix time where this time may be the time required for the UE's lower layers to be ready for an access attempt on the satellite.

The minimum time period may be received by the UE from the network using any information element (1E) or NAS message. The network may do so optionally when: * the UE indicates support for handling the minimum time period, or indicates support for behaving as described herein, or indicates a new capability that is understood to imply a UE behaviour in accordance with the proposals herein. A UE which behaves in accordance with the proposals herein should send such an indication to the network (e.g. MME, SMF, AMF, etc) using any IE or any NAS message such as a 5GMM capability IE in a Registration Request message, or any other similar IE that is sent in any EPS NAS message, * subscription information of the UE indicates that the UE supports this feature, or supports behaving in accordance with the proposals herein, or when the subscription information contains at least one minimum time value for the UE.

When the UE receives the minimum time period, where this may be per NAS mobility management, or NAS session management, or both, the UE uses the minimum time period as described earlier. Optionally, the UE may store the determined value until a new value is received or determined. Any new determined value may replace an existing determined and/or stored value in the UE.

If the minimum time period is per NAS procedure type, where the procedure may be related to either a NAS mobility management procedure or a NAS session management procedure, or both, or the minimum time period is per NAS message type, then the UE should act as follows: if the UE has a NAS procedure to initiate, then when verifying whether the UE should initiate the procedure or not (as per the proposals herein), then the UE should use the minimum time period that is associated with the NAS procedure or message, if such an association exists. Once the minimum time period has been determined, then the UE uses the minimum time period to determine whether it can initiate the NAS procedure as described herein.

The remaining time period may be received by the UE from the network. The remaining time period may be received by the UE from the network as described above with reference to the minimum time period.

The network may provide a timer value to the UE which is then used to determine if there is sufficient time for completion of the communication process. For example, the UE may determine that: * there is sufficient time if the remaining time period of the flyover time is larger (or optionally equal to or larger) than the timer value received by the UE, * there is not sufficient time if the remaining time period of the flyover time is smaller (or optionally equal to or smaller) than the timer value received by the UE.

The minimum time period may be part of UE subscription information. The minimum time period may be one value regardless of the NAS procedure, or may be per procedure or per message of the communication process, as described above. The network e.g. AMF and/or SMF, may obtain the minimum time period from the UE subscription information (e.g. from the UDM or HSS). Once obtained, the network may provide the minimum time period to the UE using the means explained above. The minimum time period may also be sent using any of a NAS message, a container, a policy container, a part of steering information, a part of roaming information.

The minimum time period may be provided to the UE by the HPLMN. The minimum time period may be provided to the UE directly using a container sent by the HPLMN in a secured manner. Once received in the UE, the UE uses the minimum time period as described herein. 5 The minimum time period may be determined by the UE. In one possibility, the minimum time period, which may or may not be associated with a specific NAS procedure/message as of the communication process described above, may be configured in the UE. The UE uses this preconfigured information to determine the minimum time period and uses the minimum time period as described herein.

The UE may store the minimum time period. The UE may continue to store the minimum time period if it is using a network access that is not the satellite access, or after the UE switches off, or after the UE deregisters from the PLMN, or changes a PLMN. Alternatively, the minimum time period may be deleted for any of the events listed and a new minimum time period may be used per PLMN once the UE registers to the PLMN. The minimum time period may be per PLMN or may apply for all PLMNs. The minimum time period may only apply for satellite access.

The proposals above may also apply to the remaining time period.

For RRC, the following problems have been identified.

Increased wastage of UE's power and resources due to procedure failure with insufficient fly-over (or remaining flyover) Considering a DC scenario used in the network and assuming that a UE is in the process of triggering a RRC procedure to communicate with the network (e.g. NG-RAN). If the satellite's flyover time is insufficient to complete the desired RRC procedure, the UE would proceed to trigger this procedure without knowing that it will be interrupted (i.e. not completed) and fail due to the UE losing coverage of the satellite. Such RRC procedure failure results in wastage of UE's power and resources in the DC scenario.

For example, assuming that a UE is trying to re-establish RRC connection with an NTN NGRAN node during a satellite flyover time in the order of minutes, and assuming that the UE initiates the RRC connection re-establishment procedure, and starts T311 timer, related to this procedure, at the last 10 seconds remaining of the satellite's fly-over time. In this case, according to TS 38.331, this RRC procedure will be interrupted (i.e. not completed) if the T311 timer value is set larger than ms10000: UE-TimersAndConstants information element This disclosure proposes solutions to avoid this problem and address the following question: How to support discontinuous coverage without excessive UE power consumption and without excessive failures / recovery actions? UE and/or network behavior if the UE deactivates its Access Stratum function This disclosure proposes solutions to avoid this problem and address the following question: What is the UE behaviour if it deactivates its Access Stratum functions in order to optimise power consumption until coverage returns? RRC procedure failure due to loss of satellite coverage Considering a DC scenario used in the network and assuming that a UE proceed to trigger a RRC procedure to communicate with the network without consideration of satellite's fly over time, the network may need to fail this procedure based on it knowledge of satellite's fly 25 overtime.

However, the UE may not understand that the RRC procedure failure is due to insufficient flyover time, and may try to repeat the RRC procedure again.

This disclosure proposes solutions to avoid this problem and address the following question:

ANT

DCONS

What is the network behaviour when rejecting an RRC procedure request from the UE in the case of DC? Network behavior following UE indication/decision of insufficient flyover time to complete procedures This disclosure proposes solutions to avoid this problem and address the following question: What is the Network behaviour if the UE informs the network that it needs to change RRC state (e.g. move to RRC IDLE) due to predicted loss of coverage? Network behavior following when a NAS message is received but the flyover time is insufficient This disclosure proposes solutions to avoid this problem and address the following question: What is the Network behaviour if the it receives a NAS message to be forwarded to the core network but the discontinuous coverage is about to start? This disclosure proposes solutions to solve the problems indicated above.

The UE verifies if there is sufficient coverage time before initiating a RRC procedure (signaling/message) The solutions in this section address the following question from problem statement: How to support discontinuous coverage without excessive UE powerconsumption and without excessive failures / recovery actions? In order to avoid the problem of wasted power and unnecessary signalling overhead between the UE and the network, as a result of incomplete RRC procedure, during a satellite's flyover time, it is proposed that the UE should first verify whether there is sufficient time to complete the desired RRC procedure, before proceeding to initiate this procedure. For example the verification may involve: * verifying if there is sufficient time for the RRC procedure to be completed before the related RRC timer expires, or * verifying if there is sufficient time, where the sufficient time may mean that there is a certain minimum time duration before the start of the next discontinuous coverage event (DC) If the UE determines that there is sufficient time (as described above), then the UE may initiate the RRC procedure.

In an alternative, the UE may determine not to initiate the procedure even if the satellite access/coverage is still available, or even if the remaining flyover time is not zero, or even if DC has not yet started. This may happen when the UE determines that there isn't sufficient time to complete the procedure.

In an alternative, in the case of multiple satellites visible to the UE, the network may configure the UE to consider the fly-over times for the multiple satellites in its decision on the sufficient time for initiating any RRC procedures. For example, the UE may select the satellite with the largest remaining fly-over time to trigger the RRC procedure with.

The proposal above is the general new behaviour that is proposed by this disclosure. The proposals that follow would describe some details that can be used to achieve the proposal above. Note that these details are meant to be as examples rather than restrictions, and they may be used in any combination or order.

The UE may determine the start time of the DC based on information provided by the network (e.g. ephemeris and/or other system information broadcast and/or dedicated signalling).

The UE may also determine the remaining time i.e. the time that remains before the start of the DC, of the flyover which is basically the time that the satellite coverage is available and hence the UE can (at least in theory) initiate a RRC procedure.

In one alternative, if the UE is already in a state which permits the UE to transmit a RRC message, then the UE may consider that it may immediately initiate the RRC procedure.

In an embodiment, the UE sends to the network indication of the UE capability to determine the remaining flyover time or to indicate to the network its capability to behave as described herein.

In an embodiment, the UE sends to the network an indication of the UE capability to handle any updated values (or extensions) of RRC procedures timers that may be impacted by DC scenarios.

In an embodiment, the UE sends to the network an indication of the UE capability not to trigger a RRC procedure(s) (signalling/message) in case of insufficient flyover period.

Alternatively, the UE sends to the network an indication of the UE capability to wait for the next satellite coverage period (i.e. satellite fly-over time) before triggering an RRC procedure.

Alternatively, the UE sends to the network an indication of the UE capability to verify the remaining fly-over time from at least one satellite.

In an embodiment, the network configures a new UE behaviour as that the UE can determine (e.g. based on calculation and/or other assistance information received from the network) whether the UE has enough time to send the desired RRC message(s) and/or signalling.

In an embodiment, the network configures the UE to not trigger an RRC signalling/message(s) if the UE determines that there is insufficient coverage time to complete a procedure (i.e. RRC signalling/message(s)) within the current fly-over period.

In an embodiment, the network configures the UE to wait for the next fly-over time before initiating an RRC procedure (i.e. RRC signalling/message(s)) , or to not attempt the RRC procedure in the current remaining flyover time, if the UE determines insufficient coverage time to complete this procedure (i.e. RRC signalling/message(s)) within the current fly-over period.

In an example, the UE may determine the remaining time before the start of the DC based of the flyover period based on information received from the network (e.g. ephmeris and/or other assistance information related to coverage timing).

In an embodiment, the UE may determine the remaining flyover time based on the UE's visibility of multiple satellite. In one alternative, the UE may select the coverage of the satellite with the longest flyover time optionally even if the conditions for selecting the satellite in terms of signalling strength, etc., are such that this satellite would not have been selected as a primary option (e.g. if another satellite should have been selected based on its signal strength, etc.). As such, the satellite selection may consider flyover time and not just signal strength, etc. i.e. not just radio conditions.

UE and/or network behavior if the UE deactivates its Access Stratum function This disclosure proposes solutions to avoid this problem and address the following question: What is the UE behaviour if it deactivates its Access Stratum functions in order to optimise power consumption until coverage returns? In one alternative, the UE which determines that there is not enough time to trigger an RRC procedure, as described above, may decide to remain in RRC_IDLE mode/state, or move to RRC_IDLE mode/state or stay in its current RRC mode/state, or any combination of these actions may be taken.

For example, assuming that the UE is in RRC_IDLE mode, and the UE determined a case of insufficient flyover time to complete an RRC procedure, e.g. RRC Resume procedure or RRC setup procedure (or any other RRC procedure), then the UE may not initiate the desired RRC procedure.

The following figures show examples of alternative UE behaviours depending on satellite flyover time: Figure 3a (Alt-1) illustrates an example of UE behaviour depending on remaining satellite fly-over time The UE receives information related to satellite's fly-over time, and/or any other timing information related to satellite coverage.

The UE determines insufficient flyover time to trigger the desired RRC procedure and The UE decides to remain in its current RRC state (e.g. RRC_IDLE mode).

For example, the UE decides not to trigger RRC re-establishment, RRC Setup, RRCResume, (or any other RRC procedure, signalling/messages).

Figure 3b (Alt-2) illustrates an example of UE behaviour depending on remaining satellite flyover time.

The UE receives information related to satellite's fly-over time, and/or any other timing information related to satellite coverage.

The UE determines insufficient flyover time to trigger the desired RRC procedure and The UE decides to remain in its current RRC state (e.g. RRC_IDLE mode), and The UE decides to trigger the RRC procedure in the next available fly-over time (or DC).

Figure 3c (Alt-3) illustrates an example of UE behaviour depending on remaining satellite fly-over time.

The UE decides to move to RRC_IDLE mode due to expected event of loss of satellite coverage in order to avoid any sudden loss of data and/or signalling loss (e.g. event of of RLF failure).

For example, the UE in RRC_CONNECTED mode or RRC_INACTIVE mode, upon verifying insufficient remaining time to transmit or receive data and/or control signalling, decides to locally release its RRC connection (i.e. move to RRC_IDLE) or request its release from the network.

RRC procedure failure due to loss of satellite coverage This disclosure proposes solutions to avoid this problem and address the following question: What is the network behaviour when rejecting an RRC procedure request from the UE in the case of DC? The UE may receive information related to satellite's flyover time and may verify that the remaining satellite fly over is insufficient to complete a desired RRC procedure, which the UE intends to trigger.

In one embodiment, the UE may ignore the insufficient flyover time, and proceed to initiate the RRC procedure. In one alternative, the UE may not verify the remaining satellite flyover time and proceed to initiate the RRC procedure that is pending.

In one alternative, the UE may not receive any information related to timing of satellite coverage (e.g. flyover time), and the UE proceed to initiate the RRC procedure. For example, the UE may send (e.g. RRC SetupRequest, RRC ReestablishmentRequest, RRCResumeRequest, etc.) without considering (or ignoring satellite flyover time, if available) to NG-RAN.

In one alternative, the UE may be configured to behave in a certain (default) way when it cannot obtain and/or calculate the remaining flyover time (or the start of the next discontinuous coverage period), or when it cannot determine if there is enough time to initiate a procedure.

For example:

* One default behaviour is that the UE does not initiate the procedure when it cannot determine the remaining time or whether there is sufficient time * One default behaviour is that the UE should initiate the procedure even if cannot determine whether there is sufficient time or not * One default behaviour is that the UE, in the event of not being able to determine whether there is sufficient time or not, can initiate the RRC procedure if the related RRC timer is less than (or equal to) a known threshold, where this threshold is either configured in the UE or received from the network. As such, the network may provide this threshold or configuration of UE behaviour using dedicated or broadcast signalling.

In order to avoid the problem of wasted power and unnecessary signalling overhead between the UE and the network, as a result of incomplete RRC procedures during a satellite's flyover time, it is proposed that the NG-RAN should verify whether there is sufficient time to complete the UE initiated RRC procedure. For example the verification may involve: * verifying if there is sufficient time for the RRC procedure to be completed before the related RRC timer expires, or * verifying if there is sufficient time, where the sufficient time may mean that there is a certain minimum time duration before the start of the next discontinuous coverage (DC) event For example, the NG-RAN determines that: * there is sufficient time if the remaining duration of the flyover time is larger (or optionally equal to or larger) than the expected duration to complete the RRC procedure * there is not sufficient time if the remaining duration of the flyover time is smaller (or optionally equal to or smaller) than the expected duration to complete the RRC procedure In the example above, the time to complete that procedure that is determined by the NG-RAN may involve determining if there is enough time for an RRC message to be processed and/or for sending a response to the UE such that the response message may arrive before the loss of coverage (or before the start of the DC period).

In an embodiment, the NG-RAN may decide to reject the UE initiated RRC procedure if the NG-RAN verifies the case of insufficient satellite flyover time to complete this RRC procedure.

In an embodiment, the NG-RAN rejects the UE initiated RRC procedure and provides a suitable new cause value for rejecting the connection. For example, NG-RAN may include a cause value "Insufficient Time to Complete Proc", "Insufficient NTN coverage Time", or any other suitable naming.

In an embodiment, the UE considers the new cause value in the reject message and may not try to trigger RLF, or any other RRC procedure until, e.g., the next satellite's fly over time is available.

Note that the NG-RAN may determine to reject the request if for example the NG-RAN determines that the RRC message would require processing such that the time to process and return a response message would not be enough. This may be determined in the NGRAN based on local configurations or may be per message type. As such, the NG-RAN may be configured to operate as described herein when certain messages are received where these messages (or procedures) may be known to require a certain minimum processing time and where the remaining flyover time may not be sufficient for the processing and/or response.

Figure 4 shows an example NG-RAN behaviour based on some of the proposals herein. Figure 4 illustrates an example of NG-RAN and UE behaviour depending on remaining satellite fly-over time.

In an embodiment, the UE may be configured to operate as follows: if the UE detects a radio link failure and needs to initiates the procedure to re-establish the RRC connection, the UE would need to verify whether sufficient flyover time is available to complete the RRC procedure before initiating this procedure. For example, the UE verifies whether remaining flyover time is enough to complete RRC re-establishment procedure.

In an embodiment, if the UE determines insufficient flyover time to complete RRC re-establishment (or RRC Connection Re-establishment) procedure, the UE may not start the RRC connection re-establishment and may move/remain in RRC_IDLE mode/state.

In another embodiment, if the UE determines insufficient flyover time to complete RRC reestablishment (or RRC Connection Re-establishment) procedure, the UE may wait for the next available satellite's flyover time before attempting a RRC connection re-establishment.

In an alternative, the UE may ignore the insufficient flyover time, and proceed to initiate the RRC re-establishment procedure. In one alternative, the UE may not verify the remaining satellite flyover time and proceed to initiate the RRC re-establishment procedure that is pending.

In an embodiment, the NG-RAN verifies if there is sufficient time to complete the RRC re-establishment procedure.

In an embodiment, the NG-RAN may determine insufficient time to complete RRC reestablishment procedure and may reject/fail the procedure, if triggered by the UE.

In an alternative, the NG-RAN may determine insufficient time to complete RRC reestablishment procedure and may reject/fail the procedure, if triggered by the UE, and optionally includes a new cause value (e.g. insufficientTimeToCompleteProc, etc.) and/or other assistant information (e.g. indication to UE to wait for the next (upcoming) satellite's flyover time, and/or other timing parameters) in the reject/failure/response message to the UE.

In an embodiment, the NG-RAN may release the UE and optionally inform the network of the UE release.

In an alternative, the NG-RAN may release the UE and optionally inform the network of the UE release and include a suitable new cause value (e.g. insufficientTimeToCompleteProc, or other) for the reason to release the UE.

All proposals, embodiments, and examples above may also apply if the UE is attempting to recover from a handover failure.

All proposals, embodiments, and examples above may also apply if the UE is attempting to recover from a other type of failure (e.g. failureType as t310-Expiry, t312-Expiry, Ibt-Failure, 15 randomAccessProblem, rIc-MaxNumRetx, beamFailure, bh-RLF, do-failure, etc.).

When the UE (or the RRC layer) determines to not re-establish its RRC connection due to RLF, or due to other failures such as handover failure, as proposed above, then the UE may enter RRC-IDLE state and may inform the upper layer (e.g. NAS) that it has entered RRCIDLE state. The RRC layer may inform the upper layer (e.g. NAS) that the reason for entering is idle state is due to insufficient time for recovery or due to DC. Alternatively the RRC layer, due to an intentional decision to not recover from RLF or other failure as described above, may not inform the upper layer (e.g. NAS) about any failure. As such, the UE should inform the upper layers (e.g. NAS) about a failure (e.g. RLF) optionally only if there is enough time to recover from the failure (as described herein) or when the UE is not using satellite access.

However if the UE is using satellite access and determines that there is not enough time to recover from a failure (e.g. RLF), then the UE does not inform the upper layer (e.g. NAS) about the failure.

Network behavior following UE indication/decision of insufficient flyover time to complete procedures This disclosure proposes solutions to avoid this problem and address the following question: What is the Network behaviour if the UE informs the network that it needs to change RRC state (e.g. move to RRC IDLE) due to predicted loss of coverage? In an embodiment, the network may configure the UE to verify whether there is sufficient time for the UE to complete RRC procedure(s), before the UE initiates a RRC procedure. In an example, the network may configure the UE using any of existing and/or newly defined signalling/message.

In an example, the NO-RAN may configure the UE to verify whether sufficient flyover time is available to complete an RRC procedure, by sending a newly defined suitable IE in any suitable existing RRC message (e.g. RRC Release, RRC Reconfiguration, or any other RRC message/signalling).

In an example, the NO-RAN may send the indication to the UE to verify whether sufficient flyover period is available to complete an RRC procedure, using system information broadcast (e.g. periodically, on-demand, other). For example, the NO-RAN may broadcast in existing SIB or in a newly defined SIB, an indication (1 bit flag) that may be set as follows: * bit ="1" , UE should verify the remaining flyover period (and/or any other timers related to RRC procedures) * bit ="0" , UE does not verify the remaining flyover period (and/or any other timers related to RRC procedures) Alternatively, the NO-RAN may configure the UE to perform RRC release, if the UE verifies that the flyovertime is not enough to complete an RRC procedure. For example, in any RRC message such as (but not limited to) the RRC Release message, the NO-RAN may include a new parameter (e.g. uEReleaselnsufficient Time 1E, uEReleaselnsufficientProcTime 1E, or any other suitable naming).

In an example, if the uEReleaselnsufficientProcTime IE is included in an RRC message e.g. the RRCRelease message (or RRCRelease with suspend configuration message), and uEReleaselnsufficientProcTime IE is set to TRUE, and UE verification outcome is that there is not enough time to perform (or complete) an RRC procedure (RRCResume, RRCSetup, other), then the UE may trigger its own RRC release or request an RRC release from the network (e.g. in order to release UE context in the network). In an embodiment, the UE may also indicate to the network the reason /cause for triggering the release (e.g. new cause value, insufficientTimeToCompleteProc, failureToCompleteProc, uEReleaseFailureToCompleteProc, other suitable naming).

In an embodiment, the network entity receiving the UE release indication (and/or the new cause/error value) may inform/forward the release request and/or the release cause to another network entity (e.g. UE sends to NG-RAN and NG-RAN forwards to AMF). The indication from the UE to the network may be carried using existing and/or newly defined signalling/messages.

In an embodiment, a UE is capable of verifying whether sufficient time is available for completing a RRC procedure. In an embodiment, a UE indicates to the network its capability to verify remaining flyover time (and/or any of the other timers discussed in this invention) to the network.

In an embodiment, the UE which determines that there is not enough flyover time as described above may deactivate its access stratum function, remain in idle mode, enter idle mode, stay in its current mode, or any combination of these actions may be taken.

In an embodiment, the UE which determines that there is not enough flyover time as described above may indicate to the network the preference to leave the RRC-CONNECTED state (or other state) and enter, e.g. idle mode, or inactive state (with suspend indication).

In another example, the UE may indicate the reason for the preference to leave the RRCCONNECTED mode/state (or other state) due to insufficient time to complete a RRC or NAS procedure.

For example, if the UE is configured to verify the remaining flyover time and indicates to the NG-RAN, its preference to leave the RRC-CONNECTED mode/state, the UE will include, e.g. a newly defined 1E, insufficientTimeToCompleteProc IE to inidicate the reason for the preference to leave RRC-CONNECTED mode/state.

Figure 5 shows an example of the UE sending an indication (e.g. insufficientTimeToCompleteProcIE) to the network (e.g. NG-RAN) for its preference to leave an RRC mode/state. Figure 5 illustrates an example of providing UE preference to move out of RRC-CONNECTED with the indication of insufficientTimeToCompleteProc IF.

For example, the NG-RAN may trigger the UE Context Release Request procedure to request the AMF to release UE context and indicate the appropriate cause value for the release, e.g. insufficientTimeToCompleteProc" (or any other suitable naming).

Figure 6 shows an example of NG-RAN including a new cause value = insufficientTimeToCompleteProc" in the UE Context Release Request procedure to request the AMF to release UE context. Figure 6 illustrates an example of including a new cause value "insufficientTimeToCompleteProc " in UE CONTEXT RELEASE REQUEST message (i.e. moving UE out of RRC_CONNECTED state).

Alternatively if the network (e.g., NG-RAN, other NW entity or NW function) and/or the UE have (has) informed the AMF that the UE is not able to complete RRC procdure(s) (e.g. due to insufficient flyover time), the AMF may trigger the release of the UE context and indicate the suitable cause value, and/or assistance information (e.g. timers mentioned in inventions above, or scalled /updated values of those timers, or other suitable timers) to the UE, e.g in the UE CONTEXT RELEASE COMMAND message, as shown in Figure 5. Figure 5 illustrates an example of including a new cause value "insufficientTimeToCompleteProc", and other assistance information in the UE CONTEXT RELEASE COMMAND message (i.e. moving UE out of RRC_CONNECTED 10 state).

All the proposals in this invention above may apply to NG-RAN, eNB, gNB and related RRC signaling/messages.

RAN2 (38.331): 5.7.4 UE Assistance Information [...] The purpose of this procedure is for the UE to inform the network of: its preference to transition out of RRC_CONNECTED state due to insufficient time for the UE to complete procedures; 5.7.4.2 Initiation A UE capable of verifying remaning satellite flytime for completion of a RRC or NAS procedure, may provide assistance information for leave indication, and may initiate the procedure if it was configured to do so upon determining that it needs to leave RRC_CONNECTED state.

New behavior for NG-RAN when handling a NAS message This disclosure proposes solutions to avoid this problem and address the following question: What is the Network behaviour if the it receives a NAS message to be forwarded to the core network but the discontinuous coverage is about to start? In an embodiment, the NG-RAN may be configured to operate as follows: the NG-RAN may receive an RRC message which includes a NAS message that should be forwarded to the core network (e.g. AM F or MME). The NG-RAN should verify if there is sufficient time such that the NAS message can be forwarded to the core network (CN). If the NG-RAN determines that there is sufficient time, then the NG-RAN should forward the message to the CN. If the NG-RAN determines that there is not sufficient time, then the NG-RAN should nor forward the message to the ON and optionally the NG-RAN may discard the message from the UE or send a response message to the UE (e.g. any existing or new RRC message, where this may be a reject message) and optionally indicate that the reason for not forwarding the message to the ON as have been proposed herein e.g. start of DC eminent, etc. The NG-RAN may include the NAS message which was not forwarded to the CN, the NG-RAN may include this message in its response to the UE.

The NG-RAN may be preconfigured with a certain threshold, or certain value which represents the threshold of a remaining flyover time before DC, which is used to determine if there is sufficient time to forward the NAS message to the ON or not. For example, if the remaining flyover time is larger than (or equal to) a known threshold, then the NG-RAN may forward the NAS message to the CN. Otherwise if the remaining flyover time is less than (or equal to) the known threshold, then the NG-RAN does not forward the NAS message to the CN.

Note that if the UE receives any RRC message with a cause code indicating that there is not sufficient time, where any other value may be used as proposed herein, then the RRC layer in the UE may indicate to the upper layer e.g. to the NAS, that there is no sufficient time and/or that DC is eminent. The RRC layer may forward to the NAS layer any NAS message which may have been received from the NG-RAN where this NAS message was a NAS message that the NG-RAN did not forward to the ON (and the NG-RAN may have sent back the NAS message to the UE).

The NG-RAN may be configured to operate as described above using operation and management, or preconfigured to behave as proposed, or the ON may configure the NG-RAN to start (or stop) operating as described above. The NG-RAN may be stop operating as described above if any of the methods used to configure the NG-RAN is used again such that the configuration indicates that the NG-RAN should not behave as proposed above.

All the proposals in this invention above may apply to NC-RAN, eNB, gNB and related RRC signaling/messages.

According to a second aspect of the present disclosure there is provided a UE in a communications network using a satellite to access the network, configured to carry out the method according to the first aspect of the present disclosure.

The UE may be configured to carry out the method when any of the following occurs, in any order or combination: * the UE is preconfigured to carry out the method, * the network indicates its support for the UE to carry out the method, where this support may be an explicit indication or an implicit indication e.g. by fact that the network provides the remaining time period or the minimum time period to the UE, * a user manually changes the settings on the UE to carry out the method.

Note that the same methods proposed herein may also be used to configure the UE to stop operating as described herein.

According to a third aspect of the present disclosure there is provided a communications network comprising a UE according to the second aspect and a core, the UE using the method according to the first aspect to access the satellite to access the core.

In a first example, there is provided a method for a UE in a communications network using a satellite to access the network, the method comprising verifying if a communication process between the UE and the satellite can be completed before expiration of a flyover time of the satellite or can not be completed before expiration of a flyover time of the satellite.

In a second example, there is provided the method according to the first example, in which the communication process is a process initiated by the UE.

In a third example, there is provided a method according to the second example, in which the communication process is a process initiated by the UE on receipt of a message from the network.

In a fourth example, there is provided a method according to any preceding example, in which the communication process comprises any of a NAS procedure, a RRC procedure.

In a fifth example, there is provided a method according to the fourth example, in which the NAS procedure is any of a NAS message, a NAS request, NAS signalling and the RRC procedure is any of a RRC message, a RRC request, RRC signalling.

In a sixth example, there is provided a method according to any preceding example, in which completion of the communication process before expiration of the flyover time of the satellite comprises the UE transmitting a message to the network.

In a seventh example, there is provided a method according to the sixth example, in which completion of the communication process before expiration of the flyover time of the satellite further comprises the UE receiving an expected response message from the network.

In an eighth example, there is provided a method according to any preceding example, the method comprising verifying if the communication process can or can not be completed before expiration of a flyover time of the satellite by using at least one time value.

In a ninth example, there is provided a method according to the eighth example, in which the time value comprises a time period before a NAS timer expires.

In a tenth example, there is provided a method according to the eighth example, in which the time value comprises a remaining time period between a current time and an expiration time of the flyover time.

In an eleventh example, there is provided a method according to the eighth example, in which the time value comprises a time period for completion of the communication process.

In a twelfth example, there is provided a method according to the tenth example and the eleventh example, the method comprising verifying that the communication process can be completed before expiration of a flyover time of the satellite by determining that the time value comprising the remaining time period is greater than the time value comprising the time period for completion of the communication process.

In a thirteenth example, there is provided a method according to the eleventh example or the twelfth example, in which the time period for completion of the communication process comprises a time period between a start of a communication procedure and an end of the communication procedure of the communication process.

In a fourteenth example, there is provided a method according to the thirteenth example, in which the time period for completion of the communication process further comprises a time period for the UE to be in a state which permits start of the communication procedure.

In a fifteenth example, there is provided a method according to the fourteenth example, in which the time period for the UE to be in a state which permits start of the communication procedure is zero if the UE is already in a state which permits the UE to start the communication procedure.

In a sixteenth example, there is provided a method according to the fourteenth example, in which the time period for the UE to be in a state which permits start of the communication procedure is non-zero and the method comprises determining the non-zero time period for the UE to be in a state which permits start of the communication procedure.

In a seventeenth example, there is provided a method according to the eighth example, in which the time value may comprise a minimum time period.

In an eighteenth example, there is provided a method according to the tenth example and the seventeenth example, the method comprising verifying that the communication process can be completed before expiration of a flyover time of the satellite by determining that the time value comprising the remaining time period is greater than or equal to the time value comprising the minimum time period.

In a nineteenth example, there is provided a method according to the seventeenth example and the eighteenth example, in which the minimum time period is received by the UE from the network.

In a twentieth example, there is provided a method according to the nineteenth example, in 25 which the minimum time period is received by the UE from the network in any of a NAS message, a container, a policy container, a part of steering information, a part of roaming information, an information element (1E).

In a twenty-first example, there is provided a method according to the seventeenth example or the eighteenth example, in which the minimum time period is part of the UE subscription information.

In a twenty-second example, there is provided a method according to the seventeenth example or the eighteenth example, in which the minimum time period is determined by the UE.

In a twenty-third example, there is provided a UE in a communications network using a satellite to access the network, wherein the UE is configured to carry out the method according to any of the first to twenty-second examples.

In a twenty-fourth example, there is provided a communications network comprising a UE according to the twenty-fourth example and a core, the UE using the method according to any of the first to twenty-second examples to access a satellite to access the core.

References [1] RP-211601, "VVID on NB-loT/eMTC support for NTN", MediaTek, RAN#92-e, June 2021 [2] 3GPP TS 36.304 [3] 3GPP TS 38.304 [4] 3GPP TS 38.331 V17 [5] 3GPP TS 38.413 V17.1.1 [6] 3GPP TS 38.304 V17 Certain examples of the present disclosure provide a computer program comprising instructions which, when the program is executed by a computer or processor, cause the computer or processor to carry out a method according to any example, embodiment, aspect and/or claim disclosed herein.

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

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

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

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

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

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

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

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

Throughout the description and claims, language in the general form of "X for Y" (where Y is some action, process, function, activity or step and X is some means for carrying out that action, process, function, activity or step) encompasses means X adapted, configured or arranged specifically, but not necessarily exclusively, to do Y. Features, elements, components, integers, steps, processes, functions, characteristics, and the like, described in conjunction with a particular aspect, embodiment, example or claim are to be understood to be applicable to any other aspect, embodiment, example or claim disclosed herein unless incompatible therewith.

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

Abbreviations/Definitions In the present disclosure, the following abbreviations and definitions may be used.

3GPP 3rd Generation Partnership Project 5G 5th Generation 5GC 5G Core AMF Access and Mobility Management Function DC Discontinuous Coverage DU Distributed Unit EPC Evolved Packet Core EMM Enterprise Mobility Management GNSS Global Navigation Satellite System GPRS General Packet Radio Service HSS Home Subscriber Server loT Internet of Things LTE Long Term Evolution MME Mobility Management Entity NAS Network Access Server NR New Radio PDU Protocol Data Unit PLMN Public/Private Land Mobile Network RAN Radio Access Network RAN2 Radio layer 2 and Radio layer 3 Working Group RRC Radio Resource Control SMF Session Management Function TTFF Time To First Fix UE User Equipment

Claims

CLAIMS1. A method of a radio access network (RAN) entity in a communications network, wherein a user equipment, (UE) uses at least one satellite to access the communications network, and wherein satellite coverage is discontinuous, the method comprising: identifying loss of satellite coverage for the UE; and in response to identifying loss of satellite coverage for the UE, releasing the UE.
2. The method of claim 1, wherein the RAN entity is an eNB, and wherein releasing the UE comprises initiating a UE context release request procedure with the serving mobility management entity (MME).
3. The method of claim 1, wherein the RAN entity is a gNB or NG-RAN, and wherein releasing the UE comprises initiating a UE context release request procedure with the access and mobility management function (AMF).
4. The method of claim 2 or 3, wherein initiating the UE context release request procedure comprises indicating that the cause of the UE release is at least one of release due to discontinuous coverage; insufficient time to complete a procedure; loss of satellite coverage; insufficient flyover time; and a start of a discontinuous coverage period.
5. The method of claim 1, wherein releasing the UE comprises releasing the UE through at least one of existing or newly defined dedicated signalling to the UE or existing or newly defined system information broadcast.
6. The method of claim 5, wherein the dedicated signalling comprises a radio resource control (RRC) release message, and wherein the RRC release message comprises a newly defined information element.
7. The method of claim 5 or 6, wherein releasing the UE comprises indicating that the cause of the UE release is at least one of: release due to discontinuous coverage; insufficient time to complete a procedure; loss of satellite coverage; insufficient flyover time; and a start of a discontinuous coverage period.
8. The method of any of claims 1 to 7, further comprising: informing the communications network of the release; wherein informing the communications network of the release comprises indicating that the cause of the UE release is at least one of: release due to discontinuous coverage; insufficient time to complete a procedure; loss of satellite coverage; insufficient flyover time; and a start of a discontinuous coverage period.
9. The method of claim 8, wherein informing the communications network of the release comprises informing the UE of the release, and indicating to the UE that the cause of the UE release is at least one of: release due to discontinuous coverage; insufficient time to complete a procedure; loss of satellite coverage; insufficient flyover time; and a start of a discontinuous coverage period.
10. A method of a radio access network (RAN) entity in a communications network, wherein a user equipment, (UE) uses at least one satellite to access the communications network, the method comprising: transmitting information to the UE, wherein the information enables the UE to determine at least one of loss of satellite coverage, start of discontinuous coverage, or remaining flyover time.
11. The method of claim 10, wherein the information is transmitted through at least one of existing or newly defined dedicated signalling or existing or newly defined system information.
12. The method of claim 11, wherein the dedicated signalling comprises a radio resource control (RRC) release message, and wherein the RRC release message comprises a newly defined information element.
13. The method of any of claims 1 to 12, further comprising receiving, from the UE, information about a UE capability, wherein the UE capability comprises at least one of: a capability to determine a remaining satellite flyover time of a satellite; a capability to support multiple satellites; a capability to determine remaining satellite flyover times of multiple satellites; a capability to handle any updated values or extensions of radio resource control (RRC) procedures timers that may be impacted by discontinuous coverage scenarios; a capability not to trigger an RRC procedure in case of insufficient flyover period a capability to wait for the next satellite coverage period before triggering an RRC 10 procedure.
14. A radio access network (RAN) entity configured to carry out the method of any of claims 1 to 13.
15. A method of a user equipment (UE) in a communications network wherein the UE uses at least one satellite to access the communications network, and wherein satellite coverage is discontinuous, the method comprising: identifying loss of satellite coverage.
16. The method of claim 15, wherein identifying loss of satellite coverage comprises at least one of: determining a start time of discontinuous coverage of the satellite; and determining a remaining time before discontinuous coverage of the satellite.
17. The method of claim 16, further comprising verifying if there is sufficient time to complete a radio resource control (RRC) procedure based on at least one of the determined start time and the determined remaining time.
18. The method of any of claims 15 to 17, further comprising: receiving information from a radio access network (RAN) entity; and identifying loss of satellite coverage based on the information.
19. The method of claim 18, wherein the information is received through at least one of existing or newly defined dedicated signalling or existing or newly defined system information.
20. The method of any of claims 15 to 19, further comprising: based on identifying loss of satellite coverage, releasing a radio resource control (RRC) connection.
21. The method of any of claims 15 to 20, further comprising indicating, to the communications network, information about a UE capability, wherein the UE capability comprises at least one of: a capability to determine a remaining satellite flyover time of a satellite; a capability to support multiple satellites; a capability to determine remaining satellite flyover times of multiple satellites; a capability to handle any updated values (or extensions) of radio resource control (RRC) procedures timers that may be impacted by discontinuous coverage scenarios; a capability not to trigger an RRC procedure in case of insufficient flyover period; and a capability to wait for the next satellite coverage period before triggering an RRC procedure.
22. The method of any of claims 15 to 21, further comprising: determining a remaining flyover time for each of a plurality of satellites; and selecting a satellite with the largest remaining flyover time among the plurality of satellites to initiate a radio resource control (RRC) procedure with.
23. A user equipment (UE) configured to carry out the method of any of claims 15 to 22.