Managing discontinuous coverage and power saving modes in NTN using timers

Abstract

In order to configure activation of a power saving mode, PSM, in a User Equipment, UE (102), a network device determines (1502) a timer value of a timer defining a period during which the UE remains active immediately after receiving the timer value prior to transitioning to the PSM. The network device transmits (1503) the timer value to the UE.

Description

Technical Field

[0001] The present disclosure relates generally to methods, apparatus, and articles of manufacture in wireless communication systems, such as 3GPP communication systems. Background Art

[0002] This background description is provided for the purpose of generally presenting the context of the present disclosure. The work of the presently named inventors, to the extent that it is described in this background section, and aspects of the specification that otherwise may not be considered prior art at the time of filing, are neither explicitly nor implicitly admitted to be prior art to the present disclosure.

[0003] The goals behind developing fifth-generation (5G) technology include providing a unified framework for communication types such as enhanced mobile broadband (eMBB), ultra-reliable low-latency communications (URLLC), and massive machine-type communications (mMTC).

[0004] 5G technology mainly relies on traditional (legacy) ground networks. However, the third generation partnership project (3GPP) organization has proposed to use 5G new radio (NR) technology or to use the long-term evolution (LTE) technology customized for narrowband Internet of Things (NB-IoT) or enhanced machine type communication (eMTC) scenarios to extend 5G communication to non-terrestrial networks (NTN). In NTN, radio frequency (RF) transceivers are installed on satellites, unmanned aircraft systems (UAS) (also known as drones, balloons, airplanes) or another suitable equipment. For simplicity, the following discussion refers to all such equipment as satellites. In addition to satellites, NTNs may also include satellites or NTN gateways (satellite gateways (sat-gateway)) that connect non-terrestrial networks to public data networks, feeder links between satellite gateways and satellites, service links between satellites, and inter-satellite links (ISLs) when satellites form constellations.

[0005] Satellites may belong to one of several types based on altitude, orbit, and beam footprint size. The types include low earth orbit (LEO) satellites, medium earth orbit (MEO) satellites, geostationary orbit (GEO) satellites, UAS platforms (including high altitude platform stations (HAPS)), and highly elliptical orbit (HEO) satellites. GEO satellites are also known as geosynchronous orbit (GSO) satellites, and LEO / MEO satellites are also known as non-GSO (NGSO) satellites.

[0006] GSO satellites can communicate with one or several satellite gateways deployed over the satellite's target coverage area (e.g., region or even continent). Non-GSO satellites can communicate with one or several serving satellite gateways at different times. NTN is designed to ensure service and feeder link continuity between consecutive serving satellite gateways, with sufficient duration for mobile anchoring and handover.

[0007] Satellites can support transparent or regenerative (with on board processing) payloads and typically generate several beams for a given service area defined by the field of view. The coverage area of ​​the beams typically has an elliptical shape and depends on the onboard antenna configuration and elevation angle. For transparent payload implementations, the satellite can apply RF filtering as well as frequency conversion and amplification without changing the waveform signal. For regenerative payload implementations, the satellite can apply RF filtering, frequency conversion and amplification, demodulation and decoding, routing, and encoding / modulation. This approach is actually equivalent to implementing most of the functions of a base station (e.g., gNB).

[0008] NB-IoT and eMTC technologies are expected to be particularly useful for IoT devices operating in remote areas with limited or no terrestrial connectivity. Such IoT devices can be used in a variety of industries, including, for example, transportation (maritime, road, rail, aviation) and logistics; solar energy, oil and gas extraction; utilities; agriculture; environmental monitoring; and mining. However, to ensure the required IoT connectivity, the deployment of these technologies requires satellite connectivity to provide coverage beyond terrestrial deployments. Satellite NB-IoT or eMTC is defined in a complementary manner to terrestrial deployments.

[0009] In these and other applications, the UE may experience discontinuous coverage in time and only have coverage occasionally. In addition, since UEs in such applications typically have limited power, the UE may operate in a power saving mode (PSM) for hours or days without a radio resource control (RRC) protocol relationship between the UE and the network. The UE may then wake up in short periods of time to notify the network of its presence and perform DL / UL transmissions for the buffered communications accumulated during the PSM. Therefore, when the time period during which the UE wakes up is not well aligned with the period of NTN coverage, the UE may miss relatively infrequent opportunities to communicate with the network and thus cause the network to prematurely deregister or detach the UE. Summary of the invention

[0010] In general, the techniques of this disclosure allow UEs to more efficiently utilize power saving mode (PSM). While in PSM, the UE has no connectivity with the network according to the protocol used to control radio resources. The UE and the network use these techniques to align UE activity time with periods of satellite coverage in order to reduce the probability that the network will prematurely deregister or detach the UE.

[0011] An example embodiment of these techniques is a method for configuring activation of PSM in a UE, the method being implemented in a network device and comprising: determining, by one or more processors, a timer value for a timer, the timer defining a period during which the UE remains active immediately after receiving the timer value and before transitioning to PSM; and transmitting, by the one or more processors, the timer value to the UE.

[0012] Another example embodiment of these techniques is a method for configuring PSM in a UE, the method being implemented in a core network and comprising: receiving, by one or more processors, a message from the UE via a non-terrestrial network (NTN); determining, by the one or more processors, that the UE will have no network coverage after expiration of a timer set to an initial value, the timer defining a period during which the UE remains in the PSM before waking up; in response to the determination, generating, by the one or more processors, an extended timer value for the timer that is greater than the initial value; and transmitting the extended timer value to the UE.

[0013] Another example embodiment is a network device comprising one or more processors and configured to implement one of the above methods.

[0014] Another embodiment of these technologies is a method for activating a power saving PSM in a UE, the method comprising: receiving, by one or more processors, a timer value from a base station connected to a core network while operating in a connected mode of a protocol for controlling radio resources; activating, by one or more processors, a timer having the timer value immediately after receiving the timer value; and transitioning to a power saving mode (PSM) after expiration of the timer.

[0015] Yet another exemplary embodiment is a UE, which includes one or more processors and is configured to implement the above method. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is a block diagram of an example wireless communication system in which user devices and base stations of the present disclosure may implement the location updating and power saving techniques of the present disclosure;

[0017] Figure 2 The centralized unit (CU) and the distributed unit (DU) can be Figure 1 A block diagram of an example base station operating in a system of FIG.

[0018] Figure 3A is a block diagram of an example NTN node with a transparent payload implementation;

[0019] Figure 3B is a block diagram of an example NTN node with a transparent payload implementation in which a base station is connected to multiple satellites via the same satellite gateway;

[0020] Figure 4A Shown is the supply Figure 3A An exemplary user plane protocol stack for use with an architecture of

[0021] Figure 4B Shown is the supply Figure 3A An exemplary control plane protocol stack for use with an architecture;

[0022] Figure 5 An example configuration is shown according to which a UE implements enhanced discontinuous reception (eDRX);

[0023] Figure 6 An example configuration is shown according to which a UE implements a power saving mode (PSM);

[0024] Figure 7 An example scenario is shown where the UE has satellite coverage during certain time periods separated by non-coverage intervals;

[0025] Fig. 8A shows an example scenario where the network deregisters a UE operating in PSM due to misalignment between UE activity time and satellite coverage;

[0026] Figure 8B An example scenario is shown in which a UE operating under PSM remains active even after leaving an area of ​​satellite coverage;

[0027] Fig. 9A and Fig. 9B is a message passing diagram for an example scenario in which the UE provides the network with the latest location information during the Attach or Tracking Area Update procedure to align the PSM configuration with the period of satellite coverage;

[0028] Fig. 10A and Fig. 10B is a messaging diagram for an example scenario in which the UE has the capability to estimate satellite coverage to align the PSM configuration with the period of satellite coverage and provide suggested timer values ​​to the network during the Attach or Tracking Area Update procedure;

[0029] Fig.11 is a message passing diagram for an example scenario in which the network extends a mobile reachable timer of a UE after determining that the PSM configuration of the UE will likely not match a period of satellite coverage;

[0030] Fig. 12Aand Fig. 12B is a flow chart of an example method for determining how to apply a PSM configuration and when to perform a TAU under PSM, which method may be implemented by a user equipment capable of obtaining its location information;

[0031] Fig.13A and Fig. 13B is a flow chart of an example method for determining how to apply a PSM configuration and when to perform a TAU under PSM, which method may be implemented by a user equipment capable of estimating / predicting satellite coverage of the present disclosure;

[0032] Fig.14 is a flow chart of an example method for initiating a process for determining whether to extend a mobile reachable timer, which method may be implemented in a network device of the present disclosure;

[0033] Fig.15 is a flowchart of an example method for configuring a UE to configure activation of a PSM, which method may be implemented in a network device of the present disclosure; and

[0034] Fig.16 is a flow chart of an example method for initiating a process for configuring activation of a PSM, which may be implemented in a UE of the present disclosure. DETAILED DESCRIPTION

[0035] As discussed in more detail below, a user equipment (UE) and / or a network node of a radio access network (RAN) may use the techniques of this disclosure to manage early data communications and to transition the UE between states of a protocol for controlling radio resources between the UE and the RAN.

[0036] First reference Figure 1 , the example wireless communication system 100 includes a UE 102, a base station (BS) 104, a base station 106, and a core network (CN) 110. The base stations 104 and 106 may operate in a RAN 105 connected to the core network (CN) 110 and other base station components such as a satellite, as will be described with reference to Figure 3A and Figure 3B CN 110 may be implemented as, for example, an evolved packet core (EPC) 111 or a fifth generation (5G) core (5GC) 160. CN 110 may also be implemented as a sixth generation (6G) core and future evolutions.

[0037] Base station 104 covers cell 124, and base station 106 covers cell 126. If base station 104 is a gNB, cell 124 is an NR cell. If base station 104 is an ng-eNB or an eNB, cell 124 is an Evolved Universal Terrestrial Radio Access (E-UTRA) cell. Similarly, if base station 106 is a gNB, cell 126 is an NR cell, and if base station 106 is an ng-eNB or an eNB, cell 126 is an E-UTRA cell. Cells 124 and 126 may be located in the same radio access network notification area (RNA) or in different RNAs. In general, RAN 105 may include any number of ground base stations and non-ground base stations, and each of the base stations may cover one, two, three, or any other suitable number of cells. UE 102 may support at least 5G NR (or simply "NR") or E-UTRA air interface to communicate with base stations 104 and 106. Each of the base stations 104, 106 may be connected to the CN 110 via an interface (eg, an S1 or NG interface). The base stations 104 and 106 may also be interconnected via an interface for interconnecting NG RAN nodes (eg, an X2 or Xn interface).

[0038] Among other components, the EPC 111 may include a serving gateway (SGW) 112, a mobility management entity (MME) 114, and a packet data network gateway (PGW) 116. In general, the SGW 112 is configured to transmit user plane packets related to audio calls, video calls, Internet traffic, etc., and the MME 114 is configured to manage authentication, registration, paging, and other related functions. The PGW 116 provides connectivity from the UE to one or more external packet data networks (e.g., an Internet network and / or an Internet Protocol (IP) Multimedia Subsystem (IMS) network). The 5GC 160 includes a user plane function (UPF) 162 and an access and mobility management function (AMF) 164 and / or a session management function (SMF) 166. In general, UPF 162 is configured to transmit user plane packets related to audio calls, video calls, Internet traffic, etc., AMF 164 is configured to manage authentication, registration, paging and other related functions, and SMF 166 is configured to manage PDU sessions.

[0039] like Figure 1 As shown, base station 104 supports cell 124, and base station 106 supports cell 126. Cells 124 and 126 may partially overlap, such that UE 102 may select, reselect, or switch from one of cells 124 and 126 to the other. Satellite base stations may provide additional RAN 105 coverage, as shown in FIG. Figure 7To exchange messages or information directly, base station 104 and base station 106 may support an X2 or Xn interface. In general, CN 110 may be connected to any suitable number of base stations supporting NR cells and / or EUTRA cells.

[0040] As discussed in detail below, when the radio connection between the UE 102 and the RAN 105 is suspended, for example, when the UE 102 is operating in an inactive or idle state of a protocol for controlling radio resources between the UE 102 and the RAN 105, the UE 102 and / or the RAN 105 can utilize the techniques of the present disclosure. For clarity, the following examples refer to the RRC_INACTIVE or RRC_IDLE states of the RRC protocol. The UE 102 can further utilize the techniques of the present disclosure when the radio connection between the UE 102 and the RAN 105 is disconnected and operating under PSM in which there is no radio resource control (RRC) protocol relationship between the UE and the network.

[0041] The base station 104 is equipped with processing hardware 130, which may include one or more general-purpose processors (e.g., CPUs) and non-transitory computer-readable memory storing instructions executed by the one or more general-purpose processors. In addition or alternatively, the processing hardware 130 may include a dedicated processing unit. In an example implementation, the processing hardware 130 includes a processor 132 to process data to be transmitted in the downlink direction by the base station 104, or to process data received in the uplink direction by the base station 104. The processing hardware 130 may also include a transmitter 136, which is configured to transmit data in the downlink direction. The processing hardware may further include a receiver 134, which is configured to receive data in the uplink direction. The base station 106 may include substantially similar components. Specifically, the components 140, 142, 144, and 146 of the base station 106 may be similar to the components 130, 132, 134, and 136, respectively.

[0042] UE 102 is equipped with processing hardware 150, which may include one or more general-purpose processors (such as CPUs) and non-transitory computer-readable memory storing machine-readable instructions that can be executed on one or more general-purpose processors, and / or a dedicated processing unit. In an example implementation, processing hardware 150 includes a processor 152 to process data to be transmitted by UE 102 in an uplink direction, or to process data received by UE 102 in a downlink direction. Processing hardware 150 may also include a transmitter 156 configured to transmit data in a downlink direction. Processing hardware may further include a receiver 154 configured to receive data in an uplink direction.

[0043] In some embodiments, the RAN 105 supports integrated access and backhaul (IAB) functionality. In some implementations, the DU 174 operates as an IAB node and the CU 172 operates as an IAB donor. In some embodiments, the RAN 105 supports non-terrestrial network (NTN) functionality.

[0044] Figure 2 An example distributed or decomposed implementation of any of the base stations 104, 106 is depicted. In this illustration, the base station 204 includes a central unit (CU) 172 and a distributed unit (DU) 174 (but the base station may include more than one DU). The CU 172 includes processing hardware, such as one or more general-purpose processors (e.g., CPUs) and a computer-readable memory storing machine-readable instructions that can be executed on the general-purpose processor, and / or a dedicated processing unit. For example, the CU 172 may include a PDCP controller, an RRC controller, and / or an RRC inactive controller. In some implementations, the CU 172 may include a radio link control (RLC) controller that is configured to manage or control one or more RLC operations or processes. In further implementations, the CU 172 does not include an RLC controller.

[0045] Similarly, DU 174 also includes processing hardware, such as one or more general purpose processors (e.g., CPUs) and computer readable memory storing machine readable instructions executable on one or more general purpose processors, and / or dedicated processing units. For example, the processing hardware may include: a MAC controller configured to manage or control one or more MAC operations or processes (e.g., random access processes); and / or an RLC controller configured to manage or control one or more RLC operations or processes. The processing hardware may also include a physical layer controller configured to manage or control one or more physical layer operations or processes.

[0046] In some implementations, the CU 172 may include a logical node CU-CP 172A that hosts a control plane portion of a PDCP protocol of the CU 172. The CU 172 may also include a logical node CU-UP 172B that hosts a user plane portion of a PDCP protocol and / or a Service Data Adaptation Protocol (SDAP) protocol of the CU 172. The CU-CP 172A may transmit control information (e.g., RRC messages, F1 application protocol messages), and the CU-UP 172B may transmit data packets (e.g., SDAP PDUs or Internet Protocol packets).

[0047] CU-CP 172A may be connected to multiple CU-UPs 172B via an E1 interface. CU-CP 172A selects an appropriate CU-UP 172B for the service requested by UE 102. In some implementations, a single CU-UP 172B may be connected to multiple CU-CPs 172A via an E1 interface. CU-CP 172A may be connected to one or more DUs 174 via an F1-C interface. CU-UP 172B may be connected to one or more DUs 174 via an F1-U interface under the control of the same CU-CP 172A. In some implementations, one DU 174 may be connected to multiple CU-UPs 172B under the control of the same CU-CP 172A. In such implementations, connectivity between CU-UP 172B and DU 174 is established by CU-CP 172A using a Bearer Context Management function.

[0048] Figure 3A A certain type of NTN deployment, referred to as a transparent payload architecture, is shown, involving a satellite gateway 302 and a "transparent" satellite 304 for extending the range of the Uu interface. The NTN deployment may be incorporated into a base station or BS 104 (or BS 106) as an extension of the Uu interface. Figure 1 The satellite 304 implements frequency conversion and radio frequency (RF) amplifiers in both the uplink and downlink directions. The satellite function is similar to that of an analog RF repeater. Therefore, the satellite 304 relays the Uu radio interface from the feeder link (between the NTN gateway and the satellite) to the service link (between the satellite and the UE) in the downlink direction, and vice versa in the uplink direction. The satellite radio interface (SRI) on the feeder link is Uu, and the NTN gateway 302 supports all functions necessary to forward the signals of the Uu interface. The NTN gateway 302 can be placed at the same site as the location of the base station (e.g., eNB, gNB) 104, or connected to the base station 104 at a certain distance via a wired link. More than one NTN gateway can also be connected to the base station. Different transparent satellites can be connected to the same base station on the ground via the same NTN gateway or via different NTN gateways. Figure 3B A situation is shown where two different satellites (304 and 306) are connected to the same base station 104 via the same NTN gateway 302 and the two satellites (304 and 306) cover the earth's surface using two different physical cell IDs (PCIs).

[0049] exist Figure 4A1 shows an NTN user plane protocol stack involving UE 102, satellite 304, NTN gateway 302, BS 104 and module 312 (i.e., S-GW 112 of EPC 111 or SMF 166 of 5GC 160). The diagram of the NTN user plane protocol stack is similar to that of the terrestrial network (TN), in which two new nodes, namely, satellite 304 and NTN gateway 302, are added and placed in the middle of the Uu interface. Similarly, Figure 4B The NTN control plane protocol stack shown is also similar to the protocol stack of the terrestrial network counterpart, where module 314 is the MME 114 of EPC111 or the AMF 164 of 5GC 160.

[0050] In terms of satellite mobility patterns, there are three types of service links supported by NTN: ● Geofixed: configured by a beam that always continuously covers the same geographical area (e.g. the case of GEO / GSO satellites) ● Quasi-geo-fixed: configured by beams that cover one geographical area during a limited period of time and a different geographical area during another period of time (e.g. the case of LEO / MEO satellites that can use steerable beams) • Geomobile: A beam configuration whereby its coverage area slides over the surface of the Earth (eg, the case of LEO / MEO satellites using fixed or unsteerable beams).

[0051] Using LEO / MEO satellites, eNB can provide quasi-Earth fixed cell coverage or Earth mobile cell coverage. Using GEO satellites, eNB can provide Earth fixed cell coverage.

[0052] although Figure 3A / Figure 3B The transparent payload architecture shown is the focus of current 3GPP development, but the regenerative payload architecture with BS functionality installed on the satellite is also a possible future NTN deployment. In this architecture, the Uu only exists between the satellite and the UE. For example, the satellite can achieve Figure 2 The functionality of DU 174. In general, the techniques of the present disclosure are applicable to transparent payload architectures as well as regenerative payload architectures.

[0053] Extended discontinuous reception (eDRX) is an extension of the DRX feature used by IoT or MTC devices to further reduce power consumption when the UE is in RRC_IDLE mode. Using the DRX mechanism, the user device can enter sleep mode for a certain period of time within RRC_IDLE mode, and then wake up after the sleep period to monitor DL ​​signals from the base station. The DRX cycle defines the time interval between two consecutive time periods when the UE wakes up. eDRX enhancement will extend the DRX cycle to allow the device to remain in sleep mode for a longer period of time. Relative to DRX mode, eDRX enhancement can be used to achieve additional power savings.

[0054] In one example, an LTE device is configured with a paging cycle (i.e., DRX cycle) of up to 2.56 seconds. With this configuration, the UE wakes up every 2.56 seconds during the paging opportunity (PO) in the paging frame (PF) and monitors for paging from the network. On the other hand, an LTE device supporting eDRX can be configured with an eDRX cycle of up to 2621.44 seconds, which allows the device to wake up once every 2621.44 seconds for a paging time window (PTW). Therefore, LTE devices supporting the eDRX feature can consume significantly less power than devices that do not support this feature. In addition, NB-IoT devices (which support eDRX by default) can be configured with an eDRX cycle of up to 10485.76 seconds, which allows the device to wake up once every 2.9 hours, and therefore, NB-IoT devices can save even more power than LTE devices supporting eDRX. Devices supporting the eDRX feature do not need to wake up for the entire PTW (ranging from 1.28 seconds to 20.48 seconds), but only wake up at paging occasions within the PTW that are determined by the legacy DRX configuration / parameters.

[0055] The UE and the network (e.g., MME or AMF) negotiate DRX and eDRX parameters using the following messages: Attach Request, Attach Accept, Tracking Area Update Request, and Tracking Area Update Accept. During the attach process, the UE provides preferred values ​​for the DRX and eDRX parameters in the Attach Request message, and the network provides the final values ​​of these parameters in the Attach Accept message. The UE may transmit an Attach Complete message to the network in response to the Attach Accept message. Similarly, during the Tracking Area Update (TAU) process, the preferred values ​​for the DRX and eDRX parameters are provided by the UE in the Tracking Area Update Request message, and the final values ​​of these parameters are provided by the network in the Tracking Area Update Accept message. The UE may transmit a TAU Complete message to the network in response to the TAU Accept message. In case of DRX configuration for non-NB-IoT devices, the network will only accept or reject the preferred DRX configuration set by the UE in the Attach Request / Tracking Area Update Request and will not provide the revised configuration in the Attach Accept / Tracking Area Update Accept message.

[0056] The DRX cycle length can be configured using the following example values: {320ms, 640ms, 1280ms, 2560ms}. For NB-IoT devices, the PTW length can be configured from the following values: {2.56s, 5.12s, 7.68s, 10.24s, 12.8s,15.36s, 17.92s, 20.48s, 23.04s, 25.6s, 28.16s, 30.72s, 33.28s, 35.84s, 38.4s,40.96s} and the eDRX cycle length can be configured from the following values: {5.12s, 10.24s, 20.48s, 40.96s,61.44s, 81.92s, 102.4s, 122.88s, 143.36s, 163.84s, 327.68s, It should be noted that if the eDRX cycle length is configured as 5.12s, the UE will not have a PTW, and the UE will only perform conventional DRX operation in which the DRX cycle length is equal to 5.12s.

[0057] Figure 5 An example is shown in which the UE is configured with an eDRX cycle equal to 20.48 seconds, a PTW equal to 5.12 seconds, and a DRX cycle equal to 1.28 seconds. In this example, the UE is configured to wake up 4 times (one paging occasion (PO) each) during the PTW in order to monitor paging messages. In addition to the PTW, the UE can completely shut down its radio module for about 15.36 seconds per eDRX cycle and thus save a lot of power.

[0058] Power saving mode (PSM) generally reduces (sometimes significantly) the power consumption of IoT devices. UEs that support PSM have more control over power management that is appropriate for their applications, which can be very advantageous because there is a wide range of IoT applications. PSM mode is generally similar to shutdown, but the UE remains registered to the network during PSM. Although the UE remains registered to the network during PSM, the UE has no radio resource control (RRC) protocol relationship with the network during PSM. Similar to the eDRX mechanism, the UE controls PSM using two timers configured through the Attach or TAU process. The first timer is T3324, which defines a time period during which the UE must remain in idle mode (and monitor paging) after transitioning from RRC_CONNECTED to RRC_IDLE. The second timer is an extended T3412 timer, which controls the periodicity (i.e., time interval) at which the UE performs periodic TAUs.

[0059] The UE may first include a T3324 value in an Attach Request message or a TAU Request message, and then the network (e.g., MME 114, or in another implementation, AMF 164) may respond to the UE with a confirmed T3324 value in an Attach Accept message or a TAU Accept message. The UE starts a timer T3324 after transitioning from a CONNECTED state to an IDLE state. After the T3324 timer expires, the UE transitions to a power saving mode. The T3324 timer defines a time period during which the device remains reachable for a mobile terminated (MT) event after transitioning from a connected state to an idle state. When the network receives T3324 in an Attach Request or a TAU Request message, the network considers its local configuration when determining the final T3324 value. In some implementations, if the T3324 value is not included in the Attach Request or the TAU Request message, the MME does not include the T3324 value in the Attach Accept or the TAU Accept message. UEs supporting the PSM feature may be used for paging while T3324 is still running. In some implementations, the network may configure T3324 with a value of "0" in the Attach Accept message or the TAU Accept message. In such implementations, the UE enters power saving mode immediately after transitioning to the RRC_IDLE state. T3324 values ​​range from 0 to 31, and the time unit is one of the following: {2 seconds, 1 minute, one tenth of an hour}.

[0060] Since T3324 is a timer running on the UE, the network starts a corresponding timer called the "Activity Timer" after determining that the UE has transitioned from the CONNECTED state to the IDLE state. The Activity Timer has the same value as T3324. While the Activity Timer is still running, the network assumes that the UE is still available for paging and accordingly pages the UE after detecting any pending MT events. When the Activity Timer expires, the network assumes that the UE has transitioned to PSM and can therefore delay paging of the UE even if there are pending MT events.

[0061] The T3412 timer is also called a periodic TAU timer. The UE performs a periodic TAU after the T3412 timer expires to periodically notify the network of the UE's availability. The UE may first include a T3412 value during the Attach or TAU process, and then the network responds to the UE with the T3412 value in the Attach Accept or Tracking Area Update Accept message. The UE applies this value when operating in all tracking areas assigned to the UE until the UE receives a new value. The UE starts the timer T3412 after transitioning to the IDLE state, and the network (e.g., MME 114, or in another implementation, AMF 164) also starts the corresponding body timer, i.e., the "mobile reachable timer", after determining that the UE has transitioned to the IDLE state. The mobile reachable timer depends on the T3412 timer, and it defaults to 4 minutes longer than the T3412 timer. When the network and the UE establish a non-access stratum NAS connection, the network stops the mobile reachable timer. After the mobile reachable timer expires, the network starts another timer called the "implicit detachment timer". If the implicit detach timer expires before the UE contacts the network, the network implicitly detaches the UE.

[0062] To support the PSM feature, a longer version of T3412 must be configured for the UE using the T3412 Extended Value IE. If the UE indicates support for an extended periodic timer value in the Attach Request or TAU Request message (e.g., via a standardized mobile station MS, network feature support information element IE), the network may also include the T3412 Extended Value IE in the Attach Accept or TAU Accept message. In addition to the T3412 extended value recommended by the UE, the network also considers local configuration when determining the final value of the T3412 extended value. If the network includes the T3412 Extended Value IE in the Attach Accept or TAU Accept message, the UE uses the value indicated in the T3412 Extended Value IE as the value of the timer T3412. The T3412 Extended Value IE contains values ​​ranging from 0 to 31, where the time unit is selected from the following set: {10 minutes, 1 hour, 10 hours, 2 seconds, 30 seconds, 1 minute, 320 hours}.

[0063] Figure 6An example is shown in which the UE is configured with a T3324 timer equal to 10 minutes and a T3412 timer equal to 1 hour. In this example, the UE performs a periodic TAU every 1 hour and stays in the connected state after performing the TAU for the duration defined by the inactivity timer. After the inactivity timer expires, the UE transitions to the IDLE state and monitors paging for the duration defined by the T3324 timer, which is 10 minutes in this example. After the T3324 timer expires, the device enters PSM and starts consuming almost no power. After T3412 expires, the device wakes up again to transition to RRC_IDLE and then performs a TAU in RRC_CONNECTED mode.

[0064] Table 1 below shows the UE timers and network timers related to the PSM feature, and the corresponding actions performed by the UE / network after these timers expire:

[0065] Figure 7 An example scenario is shown in which a LEO satellite 304 (whose position is shown at different times t1, t2, t3, t4) provides service to a UE (e.g., such as UE 102) between t1 and t2, and another LEO satellite 306 (whose position is also shown at different times t1, t2, t3, t4) provides service to the UE between t3 and t4. During the time period between t2 and t3, UE 102 is not served by any satellite or any ground base station and is therefore out of coverage. Typically, when a UE loses coverage of a serving cell, the UE begins searching for other cells and then camps on a suitable cell. However, in the Figure 7 In the example shown, even if UE 102 starts searching for other cells immediately after t2, the UE cannot find the cell, and thus searching for other cells only causes the UE to consume power. Figure 7 In order to optimize power consumption at the UE in the scenario depicted in FIG), the UE may not need to perform a cell search and may deactivate the access stratum (AS) functionality during the period when the UE is not within the coverage area of ​​the satellite. However, doing so would require the UE to know when the UE will be outside the coverage area and when the UE will be within the coverage area again, so as to reactivate its cell search or AS functionality before the UE falls within the coverage of another NTN cell. Note that Figure 7 It is not assumed that UE 102 is stationary.

[0066] Fig. 8AAn example scenario is shown in which a UE receives a PSM configuration that is not aligned with satellite coverage. In this example, the UE initially operates in RRC_CONNECTED state 802A and receives a PSM configuration that includes a T3412 value and a T3324 value. The UE releases the PSM configuration after receiving an RRC Connection Release message or after Figure 6 After the inactivity timer shown expires, it is transitioned to RRC_IDLE state 804A (also transitioned to ECM_IDLE) at t1. The UE remains in the IDLE state and monitors paging until timer T3324 expires at t2. When timer T3324 expires at t2, the UE transitions to PSM 806A. In this example, since the UE is within satellite coverage 810A, the UE can communicate with the network during the entire interval when the UE operates under CONNECTED state 802A and IDLE state 804A. Then, the UE starts timer T3412 after transitioning to the IDLE state, and the network (e.g., MME 114, or AMF 164 in another implementation) also starts a mobile reachable timer at the same time, wherein the mobile reachable timer is 4 minutes longer than T3412 in a typical implementation. (The UE remains in PSM at t3 and is not communicating within satellite coverage 812A.) In this example, due to discontinuous satellite coverage, the UE is unable to contact the network within a short time after the expiration of the mobile reachable timer (e.g., approximately 4 minutes after expiration of T3412 at the UE), and the network therefore determines to detach the UE at t4. Later at t5, the UE detects that it is within satellite coverage 814A and initiates a Radio Resource Control (RRC) connection setup procedure to send a TAU request to the network. However, since the network has detached the UE at t4 and the UE is unaware of this event, the UE wastes power at t5 trying to perform a TAU procedure 808A with the network.

[0067] Figure 8BAnother example is shown in which the UE receives a PSM configuration that is not aligned with satellite coverage. In this example, the UE initially operates in the RRC_CONNECTED state 802B and receives a PSM configuration that includes a T3412 value and a T3324 value. The UE transitions to the IDLE state 804B at t1 and starts both T3412 and T3324, and then further enters PSM 806B at t2 after T3324 expires. In this example, the UE is able to perform a TAU 808B and contact the network at t3, which occurs after T3412 expires and before the network detaches the UE, because the UE is within satellite coverage 814B at t3. However, since the UE is not within satellite coverage 814B during the entire time that timer T3324 runs, the network can attempt to reach the UE by sending one or more paging messages to the UE after t4, which paging messages are likely not to reach the UE. Such paging messages unnecessarily consume radio resources and otherwise burden the network. In this example, the UE may also need to wake up after t4 for an additional duration, which unnecessarily consumes the power of the UE. In addition, since the UE will stay in the CONNECTED state (e.g., 802B, 808B) for a duration that depends on the actual traffic situation (i.e., the duration is unpredictable), it is difficult for the network to configure and the UE to recommend an appropriate T3324 value that aligns the total UE active time with satellite coverage.

[0068] Additionally, in order to configure the UE with PSM that is aligned with the occurrence of satellite coverage, the network may need to obtain UE positioning / location information before determining the configuration. However, obtaining the location information of the UE when it is in PSM is challenging because the network cannot control the UE, and therefore, it is the UE that needs to trigger the location report.

[0069] Fig. 9A900 is a message passing diagram of an example scenario in which the UE provides its latest location information to the network in the Attach or Tracking Area Update procedure to align the PSM configuration with the period of satellite coverage; although the BSs 104, 106 are shown as eNB radio access technology satellites, the BSs 104, 106 may be implemented as any type of satellite 304, 306 that complies with 4G, 5G, 6G or future standards. The UE 102 is initially connected to the eNB 104 via a service link provided by the satellite 304 and operates in the RRC_CONNECTED state 901. Initially, the UE 102 transmits 902 a NAS message such as an ATTACH REQUEST or TAU REQUEST message to the eNB 104, and then the eNB 104 encapsulates the ATTACH REQUEST or TAU REQUEST message in an S1-AP message (i.e., a control plane message between the RAN and the core, such as an initial UE message) and forwards it 904 to the MME 114. When sending an ATTACH REQUEST or TAU REQUEST message, the UE 102 may indicate its support for extended periodic timer values ​​(via the MS Network Feature Support IE) and include the T3324 value and the T3412 extended value in the message. The UE 102 also provides its location information (e.g., its GNSS coordinates) in the ATTACH REQUEST or TAU REQUEST message. After receiving the ATTACH REQUEST or TAU REQUEST message, the MME 114 determines / calculates the period during which the UE 102 will be covered by at least one NTN cell and the period during which the UE 102 will not be covered by any NTN cell based on the satellite ephemeris information (i.e., satellite constellation information) pre-provided to or pre-installed in the MME 114, the UE location information given by the UE 102 during the ATTACH or TAU process, and some other auxiliary information (such as cell / beam coverage area size and / or antenna panel tilt). The MME 114 then determines a PSM configuration for the UE 102 that matches the period of satellite coverage determined / calculated by the MME 114 .

[0070] In response to the ATTACH REQUEST or TAU REQUEST message, the MME 114 encapsulates the ATTACH ACCEPT or TAU ACCEPT message in an initial UE message and sends it 906 to the eNB 104, and then the eNB 104 forwards the ATTACH ACCEPT or TAU ACCEPT message to the UE 102. The MME 114 provides the UE 102 with the determined PSM configuration that matches the period of satellite coverage in the ATTACH ACCEPT or TAU ACCEPT message. In one implementation, the determined PSM configuration includes a T3412 extension value IE and a UE active timer for determining when the UE 102 should transition to PSM. The UE transitions to PSM after the UE active timer expires, and the UE active timer starts immediately after the UE receives the PSM configuration from the network. Since the UE behavior with respect to the UE active timer is generally similar to that of T3324, the UE active timer may be referred to as T3324' in the remainder of this disclosure.

[0071] In one implementation, the MME 114 may include the original T3324 value IE instead of including an IE specifically defined to convey the T3324' value in the PSM configuration. In one implementation, in addition to the PSM configuration, the MME 114 also provides a distance threshold in the ATTACH ACCEPT or TAU ACCEPT message, which the UE uses to determine whether it needs to perform a TAU based on the distance it has traveled. As an alternative to the above implementation, the eNB 104 broadcasts the above distance threshold in the system information.

[0072] After receiving the ATTACH ACCEPT or TAU ACCEPT message, the UE 102 starts 909 a timer T3324'. After T3324' expires, the UE 102 then enters 910 PSM and starts a timer T3412. In some implementations, the UE 102 also starts an inactivity timer after receiving the ATTACH ACCEPT or TAU ACCEPT message, and the UE 102 then transitions to the RRC_IDLE state before transitioning to the PSM in response to the expiration of the inactivity timer. In other implementations, after receiving the ATTACH ACCEPT or TAU ACCEPT message, the UE further receives an RRCConnection Release message from the eNB 104 via the satellite 304, and transitions to the RRC_IDLE state before transitioning to the PSM in response to the RRC Connection Release message. If the UE 102 transitions to the RRC_IDLE state before transitioning to the PSM, the UE 102 starts T3412 after transitioning to the RRC_IDLE state instead of after transitioning to the PSM.

[0073] Later, the UE 102 operating under PSM is no longer within the service area of ​​the satellite 304 because the satellite 304 has moved 912 to a new location where the satellite 304 cannot provide coverage for the UE 102. Thereafter, the UE 102 detects 914 that it has traveled a distance greater than a distance threshold provided by the MME 114 or by the eNB 104. Still later, when the UE 102 detects that the satellite 306 has begun 916 to serve the area (i.e., has begun to cover the UE 102), the UE 102 performs an RRC connection setup procedure with the eNB 106 and transmits 918 a TAU REQUEST message to the eNB 106 to notify the MME 114 of the updated UE location. The UE 102 includes its location information (e.g., its GNSS coordinates) in the TAU REQUEST message and may also include a T3324 value and a T3412 extension value.

[0074] The eNB 106 forwards 920 the TAU REQUEST message to the MME 114 upon receiving the message from the UE 102, and then receives 922 a TAU ACCEPT message from the MME 114 in response to the TAU REQUEST message. The TAU ACCEPT message may include an updated T3324' value, an updated T3412 extension value, and an updated distance threshold, wherein the MME 114 determines these updated values ​​based on the updated UE location. The UE 102, upon receiving 924 the TAU ACCEPT message forwarded by the eNB 106, replaces the stored T3324' value and the T3412 extension value with the new values ​​provided in the TAU ACCEPT message, and then starts 925 a timer T3324'. After T3324' expires, the UE transitions 926 to PSM and starts the timer T3412. In some cases, the UE 102 may transition to the RRC_IDLE state before transitioning to PSM. In these cases, UE 102 will start T3412 earlier when UE 102 transitions to RRC_IDLE state. Shortly after UE 102 transitions to PSM, satellite 306 moves 928 to a new location such that satellite 306 cannot cover UE 102.

[0075] After a relatively long period of time since the UE transitioned to PSM, timer T3412 expires 930. At this point, the UE 102 needs to initiate a periodic TAU with the MME 114. In this scenario, the UE 102 waits until an upcoming satellite (e.g., satellite 304 connected to the eNB 104) begins 932 to provide service to the area where the UE 102 is currently located, and then the UE 102 transmits 934 a TAU REQUEST message to the MME 114 via the eNB 104. When sending the TAU REQUEST message, the UE 102 may indicate its support for extended periodic timer values ​​(e.g., via the MS Network Feature Support IE) and include the T3324 value, the T3412 extended value, and the UE location in the message. The eNB 104 then forwards 936 the TAU REQUEST message to the MME 114. In response to the TAU REQUEST message, the MME 114 sends 938 a TAU ACCEPT message to the UE 102 via the eNB 104, which may include an updated PSM configuration including an updated T3324' value and an updated T3412 extension value. The TAU ACCEPT message may also include an updated distance threshold used by the UE to check whether it needs to perform a TAU based on the distance it has traveled. Upon receiving 940 the TAU ACCEPT message, the UE 102 replaces the stored T3324' value and T3412 extension value with the new values ​​included in the TAU ACCEPT message, and then starts 941 the timer T3324'.

[0076] In one implementation, the MME 114 may transmit another instance of T3412 in the ATTACH ACCEPT or TAU ACCEPT message instead of the T3412 Extension Value IE. Upon receiving the ATTACH ACCEPT or TAU ACCEPT message containing this T3412 instance, the UE 102 immediately starts T3412 instead of starting this timer after the UE transitions to the RRC_IDLE state or enters PSM. In one implementation, the T3412 instance has the same value or the same value range as the T3412 Extension Value IE.

[0077] Fig. 9B 950 is a message passing diagram of another example scenario 950 in which the UE provides its latest location information to the network in the Attach or Tracking Area Update process to align the PSM configuration with the period of satellite coverage; This scenario is generally similar to scenario 900, but here the UE 102 only receives the timer value and does not receive or utilize the distance threshold. The differences between scenarios 900 and 950 are discussed below.

[0078] The MME 114 determines the T3324' value based on the factors discussed above, such as the current location of the UE 102 and the satellite ephemeris information, and transmits 907 the T3324' value in an ATTACH ACCEPT or TAU ACCEPT message to the UE 102. In this scenario, the MME 114 does not include a distance threshold in the ATTACH ACCEPT or TAU ACCEPT message transmitted 939 to the UE.

[0079] Next, Fig. 10A A messaging diagram is shown for an example scenario 1000 in which the UE informs the network of its ability to estimate satellite coverage in an Attach or Tracking Area Update procedure to align the PSM configuration with the period of satellite coverage. Although the BSs 104, 106 are shown as eNB radio access technology satellites, the BSs 104, 106 may be implemented as any type of satellite 304, 306 compliant with 4G, 5G, 6G or future standards.

[0080] UE 102 is initially connected to eNB 104 via a service link provided by satellite 304 and operates in RRC_CONNECTED state 1001. In this scenario, UE 102 is able to estimate the period of time when UE 102 will be within the coverage of at least one satellite and the period of time when UE 102 will not be covered by any satellite based on satellite ephemeris information (i.e., satellite constellation information) pre-provided to UE 102 or pre-installed in UE 102, UE location information, and some other auxiliary information provided by the network (such as cell / beam coverage size and / or antenna panel tilt). Initially, UE 102 transmits 1002 a NAS message such as ATTACHREQUEST or TAUREQUEST message to eNB 104, and then eNB 104 encapsulates the ATTACHREQUEST or TAUREQUEST message in an S1-AP message such as an initial UE message and forwards 1004 it to MME 114. When sending an ATTACH REQUEST or TAU REQUEST message, the UE 102 may indicate in the message its support for extended periodic timer values ​​(e.g., via an IMS Network Feature Support IE), and include a T3324 value and a T3412 extension value, which the UE 102 selects so that the UE 102 will be active only during periods when the UE 102 is within the coverage of at least one satellite (for monitoring paging, performing TAU, etc.). In one implementation, the UE 102 uses a dedicated IE specifically defined for conveying T3324' and / or T3412' in the ATTACH REQUEST or TAU REQUEST message, rather than using an IE defined for conveying the T3324 value and the T3412 extension value, to deliver the calibrated T3324 and T3412 values.

[0081] As an alternative to the above implementation, the UE 102 may include the T3324 value IE and the T3412 extension value IE in the ATTACH REQUEST or TAU REQUEST message to deliver the calibrated T3324 and T3412 values, and indicate to the MME 114 via an additional IE (e.g., a one-bit flag) that the UE determined the T3324 and T3412 values ​​by estimating the period of satellite coverage (i.e., the T3324 and T3412 values ​​have been calibrated).

[0082] In response to the ATTACH REQUEST or TAU REQUEST message, the MME 114 encapsulates the ATTACH ACCEPT or TAU ACCEPT message in an initial UE message and sends it 1006 to the eNB 104. The eNB 104 then forwards 1008 the ATTACH ACCEPT or TAU ACCEPT message to the UE 102. The MME 114 provides the PSM configuration determined for the UE 102 in the ATTACH ACCEPT or TAU ACCEPT message. In one implementation, the determined PSM configuration includes a T3412 extension value that "echoes" the T3412 / T3412' extension value included in the ATTACH REQUEST or TAU REQUEST message, and a T3324' value that repeats the T3324 / T3324' value included in the ATTACH REQUEST or TAU REQUEST message. In other words, the MME 114 accepts the recommendation of the UE 102. The UE 102 then enters PSM after expiration of T3324', which is initiated immediately after the UE 102 receives the PSM configuration from the network.

[0083] In some implementations, the MME 114 may include the original T3324 value IE in the PSM configuration instead of the T3324' value IE. In one implementation, in addition to the PSM configuration, the MME 114 also provides a distance threshold in the ATTACH ACCEPT or TAU ACCEPT message, which the UE 102 uses to check whether it needs to perform a TAU based on the distance it has traveled. As an alternative to the above implementation, the eNB 104 broadcasts the above distance threshold in the system information block.

[0084] After receiving the ATTACH ACCEPT or TAU ACCEPT message, the UE 102 starts 1009 a T3324' timer. After the T3324' timer expires, the UE 102 transitions 1010 to PSM and starts T3412. In some implementations, the UE 102 also starts an inactivity timer after receiving the ATTACH ACCEPT or TAU ACCEPT message, and the UE 102 then transitions to the RRC_IDLE state after the inactivity timer expires before transitioning to PSM. In other implementations, after receiving the ATTACH ACCEPT or TAU ACCEPT message, the UE further receives an RRCConnection Release message from the eNB 104 via the satellite 304, and transitions to the RRC_IDLE state before transitioning to PSM in response to the RRC Connection Release message. If the UE 102 transitions to the RRC_IDLE state before transitioning to PSM, the UE 102 starts T3412 after transitioning to the RRC_IDLE state instead of after transitioning to PSM.

[0085] Later, the UE 102 under PSM is no longer within the service area of ​​the satellite 304 because the satellite 304 has moved 1012 to a new location such that the satellite 304 cannot cover the UE 102. Thereafter, the UE 102 detects 1014 that it has traveled a distance greater than a distance threshold provided by the MME 114 or by the eNB 104. When the UE 102 detects that the satellite 306 has started 1016 serving the area (i.e., has started covering the UE 102), the UE 102 performs an RRC connection setup procedure with the eNB 106 and transmits 1018 a TAU REQUEST message to the eNB 106 to inform the MME 114 of the updated UE location. The UE 102 may include updated T3324 / T3324' values ​​and updated T3412 / T3412' extension values ​​in the TAUREQUEST message, wherein the updated T3324 / T3324' values ​​and the updated T3412 / T3412' extension values ​​are determined by the UE 102 based on new UE location information and satellite ephemeris information. In one implementation, the UE 102 also includes an additional flag, IE, or other indicator in the TAU REQUEST message to indicate whether the UE estimates the period of satellite coverage to generate the T3324 and T3412 values.

[0086] The eNB 106 forwards 1020 the TAU REQUEST message to the MME 114 upon receiving the message from the UE 102, and then receives 1022 a TAU ACCEPT message from the MME 114 in response to the TAU REQUEST message. The TAU ACCEPT message may include a T3412 extension value that repeats the T3412 / T3412' extension value transmitted in the TAU REQUEST message, a T3324' value that repeats the T3324 / T3324' value transmitted in the TAU REQUEST message, and an updated distance threshold. The UE 102, upon receiving 1024 the TAU ACCEPT message, replaces the stored T3324' value and the T3412 extension value with the new value included in the TAU ACCEPT message, and then starts 1025 a timer T3324'. After T3324' expires, the UE 102 enters 1026 PSM and starts T3412. In some cases, UE 102 may transition to the RRC_IDLE state before entering PSM. In these cases, UE 102 starts T3412 timer earlier when UE 102 transitions to the RRC_IDLE state. Shortly after UE 102 transitions to PSM, satellite 306 moves 1028 to a new location where satellite 306 cannot cover UE 102.

[0087] After the timer T3412 expires 1030, the UE 102 needs to perform a periodic TAU with the MME 114. The UE 102 waits until an upcoming satellite (e.g., the satellite 304 connected to the eNB 104) starts 1032 to provide services for the area where the UE 102 is located, and then the UE 102 transmits 1034 a TAU REQUEST to the MME 114 via the eNB 104. When sending the TAUREQUEST message, the UE 102 may indicate its support for extended periodic timer values ​​(e.g., such as via the MS Network Feature Support IE), and include a T3324 / T3324' value and a T3412 / T3412' extension value, wherein the T3324 / T3324' value and the T3412 / T3412' extension value are determined by the UE 102 based on the UE location information and the satellite ephemeris information. The UE 102 may also include an additional indication in the TAU REQUEST message to indicate whether the included T3324 and T3412 values ​​are based on the UE's estimate or prediction of the period of satellite coverage. The eNB 104 then forwards 1036 the TAU REQUEST message to the MME 114. In response to the TAUREQUEST message, the MME 114 transmits 1038 a TAU ACCEPT message to the UE 102 via the eNB 104. The message may include a T3412 extension value that repeats the T3412 / T3412' extension value included in the TAU REQUEST message, a T3324' value that repeats the T3324 / T3324' value included in the TAU REQUEST message, and an updated distance threshold. The UE 102, upon receiving 1040 the TAUACCEPT message, replaces the stored T3324' value and the T3412 extension value with the new values ​​contained in the TAU ACCEPT message, and then starts 1041 T3324'.

[0088] In one implementation, the MME 114 may transmit another instance of T3412 in the ATTACH ACCEPT or TAU ACCEPT message instead of the T3412 Extended Value IE. Upon receiving the ATTACH ACCEPT or TAU ACCEPT message containing the T3412 instance, the UE 102 starts T3412 immediately instead of after transitioning to the RRC_IDLE state or entering PSM. In one implementation, the T3412 instance has the same value or the same value range as the T3412 Extended Value IE.

[0089] Fig. 10B1050 is a message transfer diagram for another example scenario 1050 in which the UE informs the network of its ability to estimate satellite coverage in the Attach or Tracking Area Update procedure to align the PSM configuration with the period of satellite coverage. This scenario is generally similar to scenario 1000, but here the UE 102 only receives the timer value and does not receive or utilize the distance threshold. The differences between scenarios 1000 and 1050 are discussed below.

[0090] When eNB 104 then forwards 1007 the ATTACH ACCEPT or TAU ACCEPT message to UE 102, the message includes a PSM configuration that does not include a distance threshold for UE 102. In scenario 1050, UE 102 no longer detects whether the UE has traveled beyond the distance threshold (i.e., 1014 in scenario 1000 does not exist in scenario 1050). Fig. 10B Actions 1016, 1018, 1020, 1022, 1024, 1025, and 1026 are not shown in the example because they are similar to the actions in scenario 1000 (except that the NAS message TAU ACCEPT 1024 may no longer include a distance threshold). Actions 1028, 1030, 1032, 1034, 1036, 1038, and 1041 are shown in the example. Fig. 10A Scenario 1000 in FIG. 1 is performed, but the NAS message TAU ACCEPT sent 1039 from the eNB 304 to the UE 102 no longer includes the distance threshold.

[0091] Fig.11 is a messaging diagram for an example scenario in which the network extends the mobile reachable timer of the UE after determining that the UE's PSM configuration will likely not match the period of satellite coverage. UE 102 is initially connected to eNB 104 via a serving link associated with satellite 304.

[0092] In this scenario, the UE 102 lacks the capability to estimate (determine, predict) satellite coverage; the UE 102 is also unable to provide UE location information. The lack of capability may be due to, for example, the unavailability of UE GNSS coordinate information or insufficient accuracy for the UE, and / or the unavailability of satellite ephemeris information or insufficient accuracy for the UE. Initially, the UE 102 operating 1101 in RRC_CONNECTED mode transmits 1102 a NAS message such as an ATTACH REQUEST or TAU REQUEST message to the eNB 104. The eNB 104 then encapsulates the ATTACH REQUEST or TAU REQUEST message in a SI-AP message such as an initial UE message and forwards 1104 the message to the MME 114. When sending the ATTACH REQUEST or TAU REQUEST message, the UE 102 may indicate in the message its support for extended periodic timer values ​​(e.g., using an MS Network Feature Support IE, for example), and include a T3324 value and a T3412 extension value in the message. In one implementation, the UE indicates to the MME 114 via another IE that the delivered T3324 and T3412 extension values ​​are determined or selected for periods when the UE does not estimate satellite coverage.

[0093] Upon receiving the ATTACH REQUEST or TAU REQUEST, the MME 114 determines 1105 that it may not be able to provide a T3324 value and / or a T3412 extension value that causes the UE 102 to be active only during periods when the UE 102 is within the coverage of at least one satellite (for monitoring paging, performing TAU, etc.), and in response, associates the UE 102 with a mobile reachable timer that is longer than a typical setting for the timer. A typical or default setting for a mobile reachable timer may be 4 minutes greater than the T3412 extension value. In response to the ATTACH REQUEST or TAU REQUEST message, the MME 114 encapsulates an ATTACH ACCEPT or TAU ACCEPT message in an initial UE message and sends 1106 the message to the eNB 104. The eNB 104 then forwards 1108 the ATTACH ACCEPT or TAU ACCEPT message to the UE 102. The MME 114 provides the PSM configuration determined for the UE 102 including the T3412 extension value and the T3324 value in the ATTACH ACCEPT or TAU ACCEPT message.

[0094] The MME 114 may also include a distance threshold in the ATTACH ACCEPT or TAU ACCEPT message, which the UE 102 may use to determine whether it needs to perform a TAU based on the distance the UE 102 has traveled. As an alternative to the above implementation, the eNB 104 may broadcast the distance threshold in a system information block.

[0095] After sending 1108 the ATTACH ACCEPT or TAU ACCEPT message, the eNB 104 starts an inactivity timer associated with the UE 102, and then sends 1142 a S1 UE CONTEXT RELEASE REQUEST message to the MME 114 after the inactivity timer expires to release the UE context stored at the MME 114. In response to the S1 UE CONTEXT RELEASE REQUEST message, the MME 114 replies 1144 to the eNB 104 with a S1 UE CONTEXT RELEASE COMMAND message. In response to receiving the S1 UE CONTEXT RELEASE COMMAND message, the eNB 104 transmits 1146 an RRC Connection Release message to the UE 102, which causes the UE 102 to transition 1109 to the RRC_IDLE state and initiates T3412 and T3324 accordingly. Simultaneously with or shortly after the eNB 104 transmits 1146 the RRC ConnectionRelease message, the eNB 104 transmits 1148 an S1 UE CONTEXT RELEASECOMPLETE to the MME 114, which indicates the completion of the UE context release procedure and triggers the MME 114 to start 1149 a mobile reachable timer.

[0096] After T3324 expires, UE 102 enters 1110 PSM, and satellite 304 later leaves 1112 the area where UE 102 is located. Fig.11 The example in shows a situation where the UE 102 enters 1110 PSM before the satellite 304 leaves 1112 the area, but in other cases the order of these events may be reversed.

[0097] Relatively long after UE 102 enters PSM (and after satellite 304 leaves the area where UE 102 is located), timer T3412 expires 1130. At this point UE 102 needs to perform a periodic TAU as soon as possible with MME 114. UE 102 waits until an upcoming satellite (e.g., satellite 306 connected to eNB 106 in this example) starts 1116 providing service to the area where UE 102 is located, and then transmits 1134 a TAU REQUEST to MME 114 via eNB 106.

[0098] When sending the TAU REQUEST message, the UE 102 may indicate in the message its support for extended periodic timer values ​​(e.g., using an MS Network Feature Support IE) and include the T3324 value and the T3412 extended value in the message. In one implementation, the UE 102 uses a flag or another suitable IE to notify the MME 114 that the UE did not determine the values ​​of T3324 and T3412 based on an estimate of future satellite coverage. The eNB 106 forwards 1136 the received TAU REQUEST message to the MME 114.

[0099] In this example, MME 114 has associated 1105 UE 102 with a sufficiently long mobile reachable timer. Therefore, when MME 114 receives 1136 the TAU REQUEST message, the mobile reachable timer has not expired and MME 114 still has the UE context of UE 102. MME 114 may stop 1137 the mobile reachable timer and send 1138 a TAU ACCEPT message including the T3412 extension value and the T3324 value of UE 102 to eNB 106. Then, eNB 106 forwards 1140 the received TAU ACCEPT message to UE 102.

[0100] Fig. 12A is a flow chart of an example method 1200 that can be implemented in a UE (eg, UE 102 in the present disclosure) that is capable of obtaining location information (eg, GNSS coordinates) of the UE. The method 1200 is used to determine how to apply a PSM configuration and when to perform a TAU under PSM.

[0101] Initially, at block 1202, the UE has established an RRC connection with an eNB operating in the NTN and sends an ATTACH REQUEST or TAU REQUEST message containing the UE's location information to the network (i.e., MME). The UE may also include a T3412 extension value and a T3324 value in the ATTACH REQUEST or TAU REQUEST message. At block 1204, the RRC_CONNECTED UE receives an ATTACH ACCEPT or TAU ACCEPT message containing the T3412 extension value and the distance threshold. The ATTACH ACCEPT or TAU ACCEPT message may also contain a T3324 value or a T3324' value. If, at block 1206, the UE determines that the ATTACH ACCEPT or TAU ACCEPT message contains a (legacy) T3324 value, the process proceeds to block 1216, where the UE waits until it receives an RRC Connection Release message from the network or until its inactivity timer expires. Then at block 1218, the UE transitions to the RRC_IDLE state and monitors paging according to its DRX or eDRX configuration. After transitioning to the RRC_IDLE state at block 1218, the UE also starts timers T3324 and T3412. After T3324 expires, the UE transitions to PSM at block 1220, and the flow proceeds to block 1222.

[0102] On the other hand, if the UE determines at block 1206 that the ATTACH ACCEPT or TAU ACCEPT message contains a T3324' value, the flow proceeds to block 1208, where the UE starts timer T3324' immediately after receiving the ATTACH ACCEPT or TAU ACCEPT message. The flow then proceeds to block 1210, and the UE checks which of the following events occurs earlier: a) the UE receives an RRC Connection Release message from the network, b) the inactivity timer expires, or c) the timer T3324' expires. If the UE receives an RRC Connection Release message or the inactivity timer expires before the timer T3324' expires, the flow proceeds to block 1212, where the UE starts timer T3412, transitions to the RRC_IDLE state, and monitors paging according to its DRX or eDRX configuration. After T3324' expires, the UE transitions to PSM at block 1214. If the UE determines at block 1210 that timer T3324' expires before the UE receives the RRC Connection Release message and before the inactivity timer expires, flow proceeds to block 1214 where the UE transitions directly through the RRC_IDLE state, directly enters PSM, and starts timer T3412.

[0103] After entering PSM, at blocks 1222 and 1226, the UE continuously or periodically checks whether it has traveled a distance greater than a distance threshold, and also checks whether T3412 has expired. If either is true, the flow proceeds to block 1224, where the UE waits until it is covered by the upcoming / next satellite, and then establishes an RRC connection with the satellite's eNB in ​​order to perform a periodic TAU or update the network with the latest UE location information, i.e., such that the transmission of the TAU request is delayed until the UE has entered the coverage area of ​​the Radio Access Network (RAN) connected to the core network.

[0104] Fig. 12B 1 is a flow chart of an example method 1250 that is substantially similar to method 1200, but where the UE does not receive or use a distance threshold. Method 1250 includes block 1205 (instead of Fig. 12A 1204), wherein the UE operating in the RRC_CONNECTED state receives an ATTACH ACCEPT or TAU ACCEPT message containing a T3412 extension value and no distance threshold. Further, the process in method 1250 proceeds directly from block 1214 to block 1226 because Fig. 12A Unlike block 1222 of , the method does not include checking whether the UE has exceeded a threshold.

[0105] Fig.13A13 is a flow chart of an example method 1300 that can be implemented by a UE capable of estimating / predicting satellite coverage (e.g., UE 102 in the present disclosure) for determining how to apply a PSM configuration and when to perform a TAU under PSM. Initially, at box 1302, the UE has established an RRC connection with an eNB operating in an NTN and sends an ATTACH REQUEST or TAU REQUEST message to the network (i.e., MME) containing information that implies or indicates whether the UE is able to estimate / predict the period of satellite coverage. In one implementation, the UE includes an explicit indication in the ATTACH REQUEST or TAU REQUEST message to indicate whether the UE is able to estimate / predict the period of satellite coverage. In another implementation, the UE includes T3324' and / or T3412' instead of T3324 and / or T3412 in the ATTACH REQUEST or TAU REQUEST message to indicate the period of satellite coverage that the UE is able to estimate / predict. Thereafter, at box 1304, the RRC_CONNECTED UE receives an ATTACH ACCEPT or TAU ACCEPT message containing the T3412 extension value and the distance threshold. The ATTACH ACCEPT or TAU ACCEPT message may also contain a T3324 value or a T3324' value. If, at box 1306, the UE determines that the ATTACH ACCEPT or TAU ACCEPT message contains the traditional T3324 value, the process proceeds to box 1316, where the UE waits until it receives an RRC Connection Release message from the network or until its inactivity timer expires. Then at box 1318, the UE transitions to the RRC_IDLE state and monitors paging according to its DRX or eDRX configuration. After transitioning to the RRC_IDLE state at box 1318, the UE also starts timers T3324 and T3412. After T3324 expires, the UE transitions to PSM at box 1320, and the process proceeds to box 1322.

[0106] On the other hand, if the UE determines at block 1306 that the ATTACH ACCEPT or TAU ACCEPT message contains a T3324' value, the flow proceeds to block 1308, where the UE starts timer T3324' immediately after receiving the ATTACH ACCEPT or TAU ACCEPT message. The flow then proceeds to block 1310, and the UE checks which of the following events occurs earlier: a) the UE receives an RRC Connection Release message from the network, b) the inactivity timer expires, and c) the timer T3324' expires. If the UE receives an RRC Connection Release message or the inactivity timer expires before the timer T3324' expires, the flow proceeds to block 1312, where the UE starts timer T3412, transitions to the RRC_IDLE state, and monitors paging according to its DRX or eDRX configuration. After T3324' expires, the UE transitions to PSM at block 1314. If timer T3324' expires before the UE receives the RRC Connection Release message and before the inactivity timer expires at block 1310, flow proceeds to block 1314 where the UE skips the RRC_IDLE state, transitions directly to PSM, and starts timer T3412.

[0107] After entering PSM, the UE continuously or periodically checks whether it has traveled a distance greater than a distance threshold and also checks whether T3412 has expired at blocks 1322 and 1326. If either is true, the flow proceeds to block 1324 where the UE waits until it is covered by the upcoming / next satellite and then establishes an RRC connection with the satellite's eNB in ​​order to perform periodic TAUs or update the network with the UE's latest location information.

[0108] Fig. 13B 1 is a flow chart of an example method 1350 that may be implemented by a UE capable of estimating / predicting satellite coverage (e.g., UE 102 in the present disclosure) for determining how to apply a PSM configuration and when to perform a TAU under PSM. The method is generally similar to Fig.13A 1300, but here the UE does not receive or use the distance threshold. Method 1350 includes block 1305 (instead of Fig.13A 1304), wherein the UE operating in the RRC_CONNECTED state receives an ATTACH ACCEPT or TAU ACCEPT message containing a T3412 extension value and no distance threshold. Further, the process in method 1350 proceeds directly from block 1314 to block 1326 because Fig.13AUnlike block 1322 of , the method does not include checking whether the UE has exceeded a threshold.

[0109] Next, Fig.14 A flow chart of an example method 1400 that may be implemented in a network device or node (e.g., MME 114 in the present disclosure) for determining a PSM configuration and a mobile reachable timer value for a UE (e.g., UE 102 in the present disclosure) is depicted. For convenience, the method 1400 is discussed below with reference to a single network device, but more generally, the steps of the method 1400 may be distributed among any suitable number of network devices, such as an MME and one or more base stations.

[0110] Initially, at block 1402, the network device receives a TAU REQUEST or ATTACH REQUEST message from a UE and determines whether the information provided in the message is sufficient to generate a PSM configuration that matches the period of satellite coverage of the UE at block 1404. The above determination may be based on, for example, an explicit indication in the TAU REQUEST or ATTACH REQUEST message of whether the UE is able to estimate / predict the period of satellite coverage, whether the UE has provided its location information in the TAU REQUEST or ATTACH REQUEST message, or whether the UE has provided T3324' and / or T3412' instead of T3324 and / or T3412 in the TAU REQUEST or ATTACH REQUEST message. In one implementation, if the ATTACH / TAU REQUEST message includes an explicit indication indicating that the UE is able to predict / estimate the period of satellite coverage and includes a T3324 value and / or a T3412 extension value, the network device determines that the information provided in the ATTACH / TAU REQUEST message is sufficient to configure the UE with a PSM configuration that matches the period of satellite coverage. In one implementation, if the ATTACH / TAU REQUEST message includes UE location information and if the network has satellite ephemeris information, the network device determines that the information provided in the ATTACH / TAU REQUEST message is sufficient to configure the UE with a PSM configuration that matches the period of satellite coverage. In one implementation, if the ATTACH / TAU REQUEST message includes a T3324' value and / or a T3412' extension value instead of a T3324 value and / or a T3412 extension value, the network determines that the information provided in the ATTACH / TAU REQUEST message is sufficient to provide the UE with a PSM configuration that matches the period of satellite coverage.

[0111] If the network device determines that the information is insufficient at block 1404, the flow proceeds to block 1406, where the network device determines a T3412 extension value and a T3324 value for the UE. At block 1408, the network device determines a value for the UE mobile reachable timer that is independent of the determined T3412 extension value and is longer than its default setting (the conventional / default setting for the mobile reachable timer is 4 minutes greater than the T3412 extension value).

[0112] Then at box 1410, the network device sends an ATTACH / TAU ACCEPT message including a T3412 extension value, a T3324 value, and a distance threshold to the UE, and starts the UE's inactivity timer. At box 1412, after the inactivity timer expires, the network device sends an RRC Connection Release message to the UE to transition the UE to the RRC_IDLE state. At the same time, at box 1414, the network starts an activity timer with the same value as T3324 and a mobile reachable timer of the UE. As shown in box 1416, after the activity timer expires, the network interrupts paging to the UE even if there is a pending MT call / event. Shortly after the mobile reachable timer expires, the network can detach the UE from the network (i.e., release the UE context).

[0113] If the network device determines at block 1404 that the information is sufficient, flow proceeds to block 1418, where the network device determines the T3412 extension value and T3324' value of the UE, and then determines the mobile reachable timer value of the UE that depends on the T3412 extension value (e.g., the mobile reachable timer is 4 minutes greater than the T3412 extension value) at block 1420. At block 1422, the network device sends an ATTACH / TAU ACCEPT message to the UE that includes the T3412 extension value, the T3324' value, and the distance threshold.

[0114] After transmitting the ATTACH / TAU ACCEPT message, the network device starts the UE's inactivity timer at box 1424 and also starts the UE's activity timer with the same value as T3324. If the inactivity timer expires before the activity timer expires, the process proceeds to box 1426, where the network device sends an RRC Connection Release message to the UE and starts the UE's mobile reachable timer. If the activity timer expires before the inactivity timer expires, the process bypasses box 1426 and proceeds directly to box 1428, where the network device starts the UE's mobile reachable timer and interrupts paging to the UE even if there is a pending MT call / event. Shortly after the mobile reachable timer expires, the network can detach the UE from the network (i.e., release the UE context).

[0115] For further clarity, Fig.15A flow chart of an example method 1500 that may be implemented in a network device of the present disclosure or in a plurality of such devices (e.g., an MME and a base station) is depicted. At block 1502, the network device determines a timer value for a timer that defines a period during which the UE remains active immediately after receiving the timer value and before transitioning to PSM (block 1418). At block 1504, the network device transmits the timer value to the UE (events 908, 907, 1008, 1009).

[0116] Fig.16 A flow chart of an example method 1600 that can be implemented in a UE of the present disclosure is depicted. At block 1602, a UE operating in a connected mode of a protocol for controlling radio resources receives a timer value from a base station connected to a core network (events 908, 907, 1008, 1009; blocks 1204, 1205, 1304, 1305). At block 1604, the UE immediately activates a timer with the timer value upon receiving the timer value (events 909, 1009; blocks 1208, 1308). At block 1606, upon expiration of the timer, the UE transitions to PSM (events 910, 1010; blocks 1214, 1314).

[0117] According to any of the methods discussed above, before the UE determines that the UE is within the coverage of the upcoming / next satellite, the UE may turn off its radio frequency (RF) receiver or put the RF receiver into low power mode. After the UE determines that the UE is within the coverage of the upcoming / next satellite, the UE may turn on the RF receiver or transition the RF receiver to normal power mode. After turning on the RF receiver or putting the RF receiver into normal power mode, the UE receives and synchronizes the DL signal from the upcoming / next satellite, and uses the RF receiver to receive system information from the upcoming / next satellite. After receiving the system information, the UE performs a random access procedure with the upcoming / next satellite to establish an RRC connection. In other implementations, the UE may put its NTN modem (i.e., RF receiver and baseband) into low power mode before the UE determines that the UE is within the coverage of the upcoming / next satellite. After the UE determines that the UE is within the coverage of the upcoming / next satellite, the UE may transition the NTN modem to normal mode. After the NTN modem enters normal mode, the UE receives and synchronizes the DL signal from the upcoming / next satellite, and uses the NTN modem to receive system information from the upcoming / next satellite. After receiving the system information, the UE performs a random access procedure with the upcoming / next satellite to establish an RRC connection.

[0118] Although the above examples primarily involve eNBs connected to satellites 304, 306, etc., these techniques may also be used for other types of base stations, such as, for example, gNBs.

[0119] The following description can be applied to the above description.

[0120] In general, the description of one of the above figures may apply to another of the above figures. Any of the above events or boxes may be optional. For example, an event or box with a dashed line may be optional. In some implementations, "message" is used, and "message" may be replaced with "information element (IE)", and vice versa. In some implementations, "IE" is used and "IE" may be replaced with "field", and vice versa. In some implementations, "configuration" or "configuration parameter" may be replaced with "configuration", and vice versa. "eNB" may be replaced with "base station", "gNB", "6G base station", "evolved gNB" or 6G gNB. "ATTACH REQUEST" message and "ATTACHACCEPT" message may be replaced with "REGISTRATION REQUEST" message and "REGISTRATION ACCEPT" message, respectively. "MME" may be replaced with AMF or evolved AMF or 6G AMF. "RRC Connection Release message" may be replaced with "RRC Release message".

[0121] The user device (e.g., UE 102) in which the technology of the present disclosure can be implemented can be any suitable device capable of wireless communication, such as a smart phone, a tablet computer, a laptop computer, a mobile game console, a point of sale (POS) terminal, a health monitoring device, a drone, a camera, a media streaming dongle or another personal media device, a wearable device such as a smart watch, a wireless hotspot, a femtocell or a broadband router. Further, in some cases, the user device can be embedded in an electronic system, such as a head unit or an advanced driver assistance system (ADAS) of a vehicle. Still further, the user device can be operated as an Internet of Things (IoT) device or a mobile Internet device (MID). Depending on the type, the user device may include one or more general-purpose processors, a computer-readable memory, a user interface, one or more network interfaces, one or more sensors, etc.

[0122] Certain embodiments are described in the present disclosure as including logic or multiple components or modules. A module may be a software module (e.g., a code or machine-readable instruction stored on a non-transitory machine-readable medium) or a hardware module. A hardware module is a tangible unit that is capable of performing certain operations and can be configured or arranged in a particular manner. A hardware module may include a dedicated circuit system (circuitry) or logic that is permanently configured to perform certain operations (e.g., as a dedicated processor, such as a field programmable gate array (FPGA) or an application-specific integrated circuit (ASIC), a digital signal processor (DSP), etc.). A hardware module may also include programmable logic or circuit systems (e.g., as contained in a general-purpose processor or other programmable processor) that are temporarily configured by software to perform certain operations. The decision to implement a hardware module with a dedicated and permanently configured circuit system or with a temporarily configured circuit system (e.g., configured by software) may be driven by cost and time considerations.

[0123] When implemented in software, the techniques may be provided as part of an operating system, a library used by multiple applications, a specific software application, etc. The software may be executed by one or more general-purpose processors or one or more special-purpose processors.

[0124] According to a first example, a method for configuring activation of a PSM in a UE is implemented in a network device. The method includes determining a timer value of a timer, the timer defining a period during which the UE remains active immediately after receiving the timer value and before transitioning to the PSM. The method further includes transmitting the timer value to the UE.

[0125] According to a second example, the method in the first example further includes determining the current location of the UE based on the current location of the UE.

[0126] A third example is the method of the second example, wherein determining the current location of the UE includes receiving an indication of the current location from the UE.

[0127] A fourth example is a method as described in the third example, wherein the indication of the current location is received via a TAU request message.

[0128] A fifth example is the method of the third example, wherein the indication of the current location is received via an attach message.

[0129] A sixth example is a method as described in any one of the second to fifth examples, wherein the current location of the UE corresponds to a set of geographic coordinates.

[0130] A seventh example is a method as described in any one of the second to fifth examples, wherein the current location of the UE corresponds to a geographical area in which the UE is currently operating.

[0131] An eighth example is a method as described in any one of the second to seventh examples, wherein determining the timer value includes estimating future satellite coverage of the UE based on the current location of the UE and satellite ephemeris information.

[0132] The ninth example is a method as described in the first example, wherein determining the timer value includes: (1) receiving a currently configured timer value of a UE timer from the UE, the UE timer defining a time period during which the UE operates in idle mode before transitioning to PSM, and (2) determining the timer value using the currently configured timer value.

[0133] The tenth example is the method as described in the ninth example, wherein the UE timer is a T3324 timer.

[0134] An eleventh example is the method of the first example, wherein determining the timer value comprises: (1) receiving a suggested timer value, and (2) setting the timer value to the suggested timer value.

[0135] A twelfth example is the method of the eleventh example, wherein determining the timer value further comprises receiving an indication that the suggested timer value corresponds to a timer other than the T3324 timer.

[0136] A thirteenth example is the method as described in the twelfth example, wherein determining the timer value further includes receiving an indication that the UE is capable of estimating future satellite coverage.

[0137] The fourteenth example is a method as described in the first example, wherein determining the timer value further includes: determining whether to use a recommended timer value calculated at the UE to calculate the timer value based on at least one of the following: (i) an explicit indication included in a message from the UE that the UE is capable of estimating future satellite coverage, (ii) the presence of the UE's current location in the message from the UE, or (iii) the presence of a recommended timer value in the message from the UE.

[0138] The fifteenth example is a method described in any one of the first to fourteenth examples, further comprising: (1) determining a second timer value of a second timer, the second timer defining a time period during which the UE remains in PSM before waking up, and (2) transmitting the second timer value to the UE by one or more processors.

[0139] A sixteenth example is the method according to the fifteenth example, wherein the period defined by the second timer starts immediately after the UE receives the second timer value.

[0140] A seventeenth example is a method as described in the fifteenth or sixteenth example, wherein determining the second timer value includes: (1) receiving a second suggested timer value for the second timer, and (2) setting the second timer value to the suggested second timer value.

[0141] An eighteenth example is the method of the seventeenth example, wherein determining the second timer value further comprises receiving an indication suggesting that the second timer value corresponds to a second timer different from the T3412 timer.

[0142] A nineteenth example is the method as described in any one of the first to eighteenth examples, wherein the network device operates in a core network and communicates with the UE via a non-terrestrial network (NTN).

[0143] A twentieth example is the method of any one of the first to nineteenth examples, wherein transitioning to PSM includes deactivating a radio frequency (RF) receiver or transitioning the RF receiver from a normal power mode to a low power mode.

[0144] The twenty-first example is a method as described in any one of the first to nineteenth examples, wherein the transition to PSM includes reducing power consumption of the UE relative to operation in the RRC_IDLE state.

[0145] The twenty-second example is a method for configuring PSM in a UE, which is implemented in a core network. The method includes: (1) receiving a message from the UE via a non-terrestrial network (NTN); (2) determining that the UE will have no network coverage after a timer set to an initial value expires, the timer defining a period during which the UE remains in PSM before waking up; (3) in response to the determination, generating an extended timer value of the timer, the extended timer value being greater than the initial value; and (4) transmitting the extended timer value to the UE.

[0146] The twenty-third example is the method as described in the twenty-second example, wherein receiving a message from the UE includes receiving a TAU request message.

[0147] The twenty-fourth example is the method as described in the twenty-second example, wherein receiving the message from the UE includes receiving an attach message.

[0148] The twenty-fifth example is a method as described in the twenty-third or twenty-fourth example, wherein the message includes location information of the UE, and the method further includes generating the extended timer value based on the location information.

[0149] A twenty-sixth example is the method of the twenty-fifth example, wherein generating the extended timer value is further based on satellite ephemeris information.

[0150] The twenty-seventh example is the method as described in the twenty-second example, wherein the timer is a T3412 timer.

[0151] A twenty-eighth example is the method of the twenty-second to twenty-seventh examples, wherein transitioning to PSM includes deactivating a radio frequency (RF) receiver or transitioning the RF receiver from a normal power mode to a low power mode.

[0152] A twenty-ninth example is the method as described in any of the twenty-second to twenty-seventh examples, wherein the transitioning to the PSM includes reducing power consumption of the UE relative to operation in the RRC_IDLE state.

[0153] The thirtieth example is a network device, which includes one or more processors and is configured to implement the method of any one of the preceding examples.

[0154] The thirty-first example is a method for activating PSM in a UE, the method being performed by the UE. The method includes: (1) when the UE is operating in a connection mode of a protocol for controlling radio resources, receiving a timer value from a base station connected to a core network; (2) immediately activating a timer having the timer value after receiving the timer value; and (3) after the timer expires, transitioning to PSM.

[0155] The thirty-second example is a method as described in the thirty-first example, further comprising: transmitting the current UE location information to the core network before receiving the timer value.

[0156] The thirty-third example is a method as described in the thirty-second example, wherein transmitting the current UE location information includes transmitting a TAU request message.

[0157] The thirty-fourth example is a method as described in the thirty-second example, wherein transmitting the current UE location information includes transmitting an attach message.

[0158] The thirty-fifth example is a method as described in any one of the thirty-first to thirty-fourth examples, wherein the current UE location information corresponds to a set of geographic coordinates.

[0159] The thirty-sixth example is a method as described in any one of the thirty-first to thirty-fourth examples, wherein the current UE location information corresponds to a geographical region in which the UE is currently operating.

[0160] The thirty-seventh example is a method as described in any one of the thirty-first to thirty-sixth examples, further comprising: before receiving the timer value, transmitting a currently configured timer value of a UE timer to the core network, wherein the UE timer defines a time period during which the UE operates in idle mode before transitioning to PSM.

[0161] The thirty-eighth example is a method as described in the thirty-seventh example, wherein the UE timer is a T3324 timer.

[0162] The thirty-ninth example is a method as described in the thirty-first example, further including: (1) estimating future satellite coverage of the UE; (2) generating a recommended timer value for the timer based on the future satellite coverage; and (3) transmitting the recommended timer value to the core network before receiving the timer value.

[0163] The 40th example is a method as described in the 39th example, further comprising: before receiving the timer value, transmitting to the core network an indication that the UE is capable of estimating future satellite coverage.

[0164] The forty-first example is a method as described in any one of the thirty-first to fortieth examples, wherein the base station operates in a non-terrestrial network (NTN).

[0165] The forty-second example is a UE comprising one or more processors and configured to implement a method as described in any one of the thirty-first to forty-first examples.

[0166] The forty-third example is a method for configuring activation of PSM in a UE, the method being implemented in a network device. The method includes: (1) using the current location of the UE to determine a timer value of a timer, the timer defining a period during which the UE remains active before transitioning to PSM; and (2) transmitting the timer value to the UE.

[0167] The forty-fourth example is a method as described in the forty-third example, further comprising: estimating the network coverage of the UE based on the current location of the UE, and determining the timer value is based on the estimated network coverage.

[0168] The forty-fifth example is the method as described in the forty-fourth example, wherein the estimated network coverage is NTN coverage.

[0169] The forty-sixth example is a method as described in the forty-third example, wherein the estimation of the network coverage of the UE is performed using satellite ephemeris information.

[0170] The forty-seventh example is a method as described in any one of the forty-third to forty-sixth examples, wherein the timer is configured to start immediately after the UE receives the timer value.

Claims

1. A method (1500) performed by a network device (140) of a core network (110), the method for configuring activation of a power saving mode (PSM) in a user equipment (102) UE connected to the core network via a non-terrestrial network (105) NTN, the method comprising: determining (1502) a timer value for a timer, the timer defining a period during which the UE remains active immediately after receiving the timer value and before transitioning to the PSM; as well as The timer value is transmitted (1504) to the UE.

2. The method of claim 1, further comprising: obtaining the current location of the UE, The determination of the timer value is based on the current location of the UE.

3. The method of claim 2, wherein: Obtaining the current location of the UE includes: A tracking area update (TAU) request message or an attach request message is received from the UE, wherein the TAU request message or the attach request message includes an indication of the current location.

4. The method according to any one of claims 2 or 3, wherein: Determining the timer value includes evaluating the NTN coverage based on the current location of the UE and satellite ephemeris information.

5. The method according to any one of claims 1 to 4, further comprising: receiving, from the UE, a currently configured timer value of a UE timer, the UE timer defining a UE time period during which the UE operates in an idle mode prior to transitioning to the PSM; as well as The timer value is determined using the currently configured timer value.

6. The method according to any one of claims 1 to 5, wherein: Determining the timer value includes: receiving a suggested timer value from the UE; and The timer value is set to the suggested timer value.

7. The method of claim 6, wherein: Determining the timer value further comprises: An indication is received that the UE is capable of estimating the NTN coverage.

8. The method according to any one of claims 1 to 7, further comprising: determining a second timer value for a second timer, the second timer defining a PSM period during which the UE remains in the PSM; as well as The second timer value is transmitted to the UE.

9. The method of claim 8, wherein: Determining the second timer value includes: receiving a second suggested timer value from the UE; and If it is estimated that the UE will be out of the NTN coverage when the second recommended timer expires, the second timer value is set to an extended timer value longer than the recommended second timer value.

10. The method of claim 9, further comprising: Obtaining location information of the UE; as well as The extended timer value is generated using the location information.

11. The method of claim 10, wherein: Generating the extended timer value further uses satellite ephemeris information.

12. A network device (140) connected to a user equipment (102) UE via a non-terrestrial network (105) NTN, the network device comprising a transceiver (144, 146), a processor (142) and a computer-readable storage medium, the computer-readable storage medium storing executable instructions for the processor to use the transceiver to perform any of the methods of claims 1 to 11.

13. A method (1600) performed by a UE connected to a core network (110) via a non-terrestrial network (105) NTN, the method for activating a power saving mode PSM, the method comprising: receiving a timer value from the core network via the NTN; activating a timer having the timer value immediately upon receiving the timer value; as well as After expiration of the timer, a transition is made to a power saving mode (PSM).

14. The method of claim 13, further comprising: Before receiving the timer value, current UE location information is transmitted to the core network.

15. The method of any one of claims 13 or 14, further comprising: Prior to receiving the timer value, transmitting, via the NTN, to the core network a currently configured timer value for a UE timer, the UE timer defining a time period during which the UE operates in an idle mode prior to transitioning to the PSM.

16. The method of any one of claims 13 to 15, further comprising: generating a suggested timer value using the estimated NTN coverage; as well as Prior to receiving the timer value, transmitting the suggested timer value to the core network.

17. The method of any one of claims 13 to 16, further comprising: Prior to receiving the timer value, an indication is transmitted to the core network via the NTN that the UE is capable of estimating NTN coverage.

18. A user equipment UE (102), the UE comprising a transceiver (154, 156), a processor (152) and a computer-readable storage medium, the computer-readable storage medium storing executable instructions for the processor to use the transceiver to perform any of the methods of claims 13 to 17.

Images