Mechanism to start connection release protection timer when disaster roaming is rejected

Abstract

A UE sends a non-access stratum (NAS) request message to a core network of a public land mobile network (PLMN) used for disaster, the NAS request message requesting disaster roaming service for a determined PLMN with a disaster condition. The UE receives a NAS reject message from the core network, the NAS reject message including a cause value indicating that disaster roaming for the determined PLMN with the disaster condition is not allowed. The UE starts a protection timer in response thereto. The protection timer provides a predetermined time length for the core network to release a NAS signaling connection. When a connection release command is not received from the core network before the protection timer expires, the UE performs a local release of the NAS signaling connection upon expiration of the protection timer. When the connection release command is received from the core network before the protection timer expires, the UE stops the protection timer and releases the NAS signaling connection.

Description

[0001] Cross-referencing

[0002] This application claims priority to Indian Patent Application No. 202421077303, filed on October 11, 2024, entitled “METHOD TO START CONNECTION RELEASE GUARD TIMER DUE TOREJECT FOR DISASTER ROAMING”, the entire contents of which are expressly incorporated herein by reference. Technical Field

[0003] This disclosure generally relates to wireless communications, and more specifically, to techniques for managing the release of non-access stratum (NAS) signaling connections using a protection timer when a disaster roaming request is denied, in order to maintain synchronization between user equipment (UE) and the network across multiple generations of cellular systems, including 4G, 5G, and 6G. Background Technology

[0004] The statements in this section are provided only as background information in connection with this disclosure and may not constitute prior art.

[0005] Wireless communication systems are widely deployed to provide a variety of telecommunications services, such as telephone, video, data, messaging, and broadcasting. Typical wireless communication systems employ multiple access technologies that enable communication with multiple users by sharing available system resources. Examples of such multiple access technologies include code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, orthogonal frequency division multiple access (OFDMA) systems, single-carrier frequency division multiple access (SC-FDMA) systems, and time division synchronous code division multiple access (TD-SCDMA) systems.

[0006] These multiple access technologies have been adopted in various telecommunications standards to provide a common protocol enabling different wireless devices to communicate at the city, national, regional, and even global levels. An exemplary telecommunications standard is 5G New Radio (NR). 5G NR is part of the continuous evolution of mobile broadband promoted by the Third Generation Partnership Project (3GPP) to meet new requirements associated with latency, reliability, security, scalability (e.g., related to the Internet of Things (IoT),) and other requirements. Some aspects of 5G NR can be based on the 4G Long Term Evolution (LTE) standard. There is a need for further improvements to 5G NR technology. These improvements can also be applied to other multiple access technologies and telecommunications standards that adopt them. Summary of the Invention

[0007] The following is a simplified overview of one or more aspects to provide a basic understanding of such aspects. This overview is not an exhaustive summary of all conceptual aspects, nor is it intended to identify key or important elements of all aspects, nor to define the scope of any or all aspects. Its sole purpose is to present some concepts of one or more aspects in a simplified form as a prelude to the more detailed descriptions that follow.

[0008] In one aspect of this disclosure, a method, a computer-readable medium, and an apparatus are provided. The apparatus may be a UE (User Equipment). The UE sends a NAS (Disaster Navigation Request) message to the core network of a public land mobile network (PLMN) for disaster use, the NAS request message requesting disaster roaming services for a determined PLMN with a disaster condition. The UE receives a NAS rejection message from the core network, the NAS rejection message including a reason value indicating that disaster roaming is not permitted for the determined PLMN with the disaster condition. In response to receiving the NAS rejection message with the reason value, the UE starts a protection timer. The protection timer provides the core network with a predetermined duration for releasing the NAS signaling connection. If no connection release command is received from the core network before the protection timer expires, the UE performs a local release of the NAS signaling connection when the protection timer expires. If the connection release command is received from the core network before the protection timer expires, the UE stops the protection timer and releases the NAS signaling connection.

[0009] To achieve the foregoing and related objectives, the one or more aspects include features fully described below and specifically pointed out in the claims. Certain illustrative features of the one or more aspects are set forth in detail in the following description and the accompanying drawings. However, these features indicate only a few of the various ways in which the principles of each aspect may be employed, and this description is intended to include all such aspects and their equivalents. Attached Figure Description

[0010] Figure 1 This is a schematic diagram illustrating an example of a wireless communication system and an access network.

[0011] Figure 2 This is a schematic diagram showing a base station communicating with the UE in the access network.

[0012] Figure 3 This illustrates an example logical architecture for a distributed access network.

[0013] Figure 4 An example physical architecture of a distributed access network is shown.

[0014] Figure 5 This is a schematic diagram illustrating the communication between the UE, the regular PLMN, and the disaster recovery PLMN.

[0015] Figure 6 This is a flowchart of a method for managing connection release after a disaster roaming is denied. Detailed Implementation

[0016] The detailed description set forth below in conjunction with the accompanying drawings is intended as a description of various configurations, and not as representing the only configuration in which the concepts described herein can be practiced. This detailed description includes specific details used to provide a thorough understanding of the various concepts. However, it will be apparent to those skilled in the art that these concepts can be practiced without these specific details. In some instances, well-known structures and components are shown in block diagram form to avoid obscuring such concepts.

[0017] Several aspects of a telecommunications system will now be presented with reference to various devices and methods. These devices and methods will be described in detail below and illustrated in the accompanying drawings by various blocks, components, circuits, programs, algorithms, etc. (collectively, “elements”). These elements may be implemented using electronic hardware, computer software, or any combination thereof. Whether such elements are implemented as hardware or software depends on the specific application and the design constraints imposed on the system as a whole.

[0018] For example, an element, any part of an element, or any combination of elements may be implemented as a "processing system" including one or more processors. Examples of processors include microprocessors, microcontrollers, graphics processing units (GPUs), central processing units (CPUs), application processors, digital signal processors (DSPs), reduced instruction set computing (RISC) processors, systems on a chip (SoCs), baseband processors, field-programmable gate arrays (FPGAs), programmable logic devices (PLDs), state machines, gated logic, discrete hardware circuitry, and other suitable hardware configured to perform the various functions described throughout this disclosure. One or more processors in the processing system can execute software. Software should be interpreted broadly to mean instructions, instruction sets, code, code segments, program code, programs, subroutines, software components, applications, software applications, software packages, routines, subroutines, objects, executable files, execution threads, procedures, functions, etc., regardless of whether it is called software, firmware, middleware, microcode, hardware description languages, or other names.

[0019] Therefore, in one or more example aspects, the described functionality can be implemented in hardware, software, or any combination thereof. If implemented in software, these functions can be stored or encoded / decoded on a computer-readable medium as one or more instructions or code. Computer-readable media include computer storage media. Storage media can be any available medium accessible by a computer. By way of example, and not limitation, such computer-readable media can include random-access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), optical disk storage, magnetic disk storage, other magnetic storage devices, combinations of computer-readable media of the types described above, or any other medium that can be used to store computer-executable code in the form of instructions or data structures accessible by a computer.

[0020] Figure 1This is a schematic diagram illustrating an example of a wireless communication system and access network 100. The wireless communication system (also known as a wireless wide area network (WWAN)) includes a base station 102, a user interface unit (UE) 104, an evolved packet core (EPC) 160, and another core network 190 (e.g., a 5G core network (5GC)). The base station 102 may include macro cells (high-power cellular base stations) and / or small cells (low-power cellular base stations). Macro cells include base stations. Small cells include nanocells, picocells, and microcells.

[0021] Base station 102 configured for 4G LTE (collectively referred to as the Evolved UMTS Terrestrial Radio Access Network, E-UTRAN) can interface with EPC 160 via backhaul link 132 (e.g., SI interface). Base station 102 configured for 5G NR (collectively referred to as the Next Generation RAN, NG-RAN) can interface with core network 190 via backhaul link 184. Among other functions, base station 102 may perform one or more of the following functions: transmission of user data, encryption and decryption of radio channels, integrity protection, header compression, mobility control functions (e.g., handover, dual connectivity), inter-cell interference coordination, connection establishment and release, load balancing, distribution of non-access stratum (NAS) messages, NAS node selection, synchronization, radio access network (RAN) sharing, multimedia broadcast multicast service (MBMS), subscriber and device tracking, RAN information management (RIM), paging, location, and delivery of warning messages. Base stations 102 may communicate with each other directly or indirectly (e.g., via EPC 160 or core network 190) via backhaul link 134 (e.g., X2 interface). Backhaul link 134 may be wired or wireless.

[0022] Base station 102 can wirelessly communicate with UE 104. Each of base stations 102 can provide communication coverage for a corresponding geographic coverage area 110. There may be overlapping geographic coverage areas 110. For example, small cell 102' may have a coverage area 110' that overlaps with the coverage areas 110 of one or more macro base stations 102. A network that includes both small cells and macro cells can be called a heterogeneous network. The heterogeneous network may also include Home Evolved Node B (HeNB), which can provide services to restricted groups called closed subscriber groups (CSG). The communication link 120 between base station 102 and UE 104 may include uplink (UL) (also known as reverse link) transmission from UE 104 to base station 102 and / or downlink (DL) (also known as forward link) transmission from base station 102 to UE 104. Communication links 120 may use multiple-input multiple-output (MIMO) antenna techniques, including spatial multiplexing, beamforming, and / or transmit diversity. These communication links may be carried out via one or more carriers. Base station 102 / UE 104 may use spectrum with a bandwidth of up to 7 MHz per carrier (e.g., 5, 10, 15, 20, 100, 400 MHz, etc.), which is allocated in carrier aggregation totaling up to Yx MHz (x component carriers) for transmission in each direction. These carriers may be adjacent to each other or not. The allocation of carriers relative to DL and UL may be asymmetric (e.g., more or fewer carriers may be allocated to DL than to UL). These component carriers may include a primary component carrier and one or more secondary component carriers. The primary component carrier may be referred to as the primary cell (PCell), and the secondary component carriers may be referred to as secondary cells (SCells).

[0023] Some UEs 104 can communicate with each other using device-to-device (D2D) communication links 158. D2D communication links 158 can use DL / UL WWAN spectrum. D2D communication links 158 can use one or more sidelink channels, such as the physical sidelink broadcast channel (PSBCH), physical sidelink discovery channel (PSDCH), physical sidelink shared channel (PSSCH), and physical sidelink control channel (PSCCH). D2D communication can be performed through various wireless D2D communication systems, such as FlashLinQ, WiMedia, Bluetooth, ZigBee, Wi-Fi based on the IEEE 802.11 standard, LTE, or NR.

[0024] The wireless communication system may also include a Wi-Fi access point (AP) 150, which communicates with a Wi-Fi station (STA) 152 via a communication link 154 in the 5 GHz unlicensed spectrum. When communicating in the unlicensed spectrum, the STA 152 / AP 150 may perform a clear channel assessment (CCA) before communication to determine whether the channel is available.

[0025] Cell 102' can operate in licensed and / or unlicensed spectrum. When operating in unlicensed spectrum, cell 102' can employ NR and use the same 5 GHz unlicensed spectrum as Wi-Fi AP 150. Employing NR in unlicensed spectrum can improve coverage and / or increase the capacity of the access network.

[0026] Base station 102 (whether it's a small cell 102' or a large / small cell (e.g., a macro base station)) may include an eNB, gNodeB (gNB), or another type of base station. Some base stations (e.g., gNB 180) may communicate with UE 104 on conventional sub-6 GHz spectrum, millimeter wave (mmW) frequencies, and / or near-millimeter wave frequencies. When gNB 180 operates on millimeter wave or near-millimeter wave frequencies, gNB 180 may be referred to as a millimeter wave base station. Extremely high frequency (EHF) is a radio frequency component of the electromagnetic spectrum. EHF ranges from 30 GHz to 300 GHz, with wavelengths between 1 mm and 10 mm. Radio waves in this band may be referred to as millimeter waves. Near-millimeter waves extend down to frequencies up to 3 GHz, with wavelengths of 100 mm. The ultra-high frequency (SHF) band extends between 3 GHz and 30 GHz and is also known as centimeter waves. Communication using millimeter-wave / near-millimeter-wave radio frequency bands (e.g., 3 GHz to 300 GHz) has extremely high path loss and extremely short transmission distance. Millimeter-wave base station 180 can work with UE 104 to utilize beamforming 182 to compensate for the extremely high path loss and extremely short transmission distance.

[0027] Base station 180 may transmit beamforming signals to UE 104 in one or more transmit directions 108a. UE 104 may receive the beamforming signals from base station 180 in one or more receive directions 108b. UE 104 may also transmit beamforming signals to base station 180 in one or more transmit directions. Base station 180 may receive the beamforming signals from UE 104 in one or more receive directions. Base station 180 / UE 104 may perform beam training to determine the optimal receive and transmit directions for each of base station 180 / UE 104. The transmit and receive directions of base station 180 may be the same or different. The transmit and receive directions of UE 104 may be the same or different.

[0028] EPC 160 may include a Mobility Management Entity (MME) 162, other MMEs 164, a Serving Gateway 166, a Multimedia Broadcast Multicast Service (MBMS) Gateway 168, a Broadcast Multicast Service Center (BM-SC) 170, and a Packet Data Network (PDN) Gateway 172. MME 162 can communicate with the Home Subscriber Server (HSS) 174. MME 162 is the control node that handles signaling between UE 104 and EPC 160. Generally, MME 162 provides bearer management and connection management. All user Internet Protocol (IP) packets are transmitted through the Serving Gateway 166, which is itself connected to the PDN Gateway 172. The PDN Gateway 172 provides UE IP address allocation and other functions. The PDN Gateway 172 and BM-SC 170 are connected to the IP service 176. IP service 176 may include the Internet, intranet, Internet Protocol Multimedia Subsystem (IMS), packet-switched (PS) streaming media services, and / or other IP services. BM-SC 170 provides functions for providing and delivering MBMS user services. BM-SC 170 can serve as an entry point for MBMS transmission by content providers, can be used to authorize and initiate MBMS bearer services within a public land mobile network (PLMN), and can be used to schedule MBMS transmissions. MBMS gateway 168 can be used to distribute MBMS traffic to base station 102 in a Multicast Broadcast Single Frequency Network (MBSFN) area belonging to broadcast-specific services, and can be responsible for session management (start / stop) and collecting eMBMS-related billing information.

[0029] The core network 190 may include an Access and Mobility Management Function (AMF) 192, other AMFs 193, a location management function (LMF) 198, a Session Management Function (SMF) 194, and a User Plane Function (UPF) 195. The AMF 192 can communicate with the Unified Data Management (UDM) 196. The AMF 192 is the control node that handles signaling between the UE 104 and the core network 190. Generally, the SMF 194 provides Quality of Service (QoS) flow management and session management. All user IP packets are transmitted through the UPF 195. The UPF 195 provides UE IP address allocation and other functions. The UPF 195 connects to IP services 197. IP services 197 may include the Internet, intranets, IMS, PS streaming services, and / or other IP services.

[0030] A base station may also be referred to as a gNB, Node B, eNB, access point, base transceiver station, wireless base station, wireless transceiver, transceiver function, basic service set (BSS), extended service set (ESS), transmit reception point (TRP), or some other suitable terminology. Base station 102 provides UE 104 with access to EPC 160 or core network 190. Examples of UE 104 include cellular phones, smartphones, session initiation protocol (SIP) phones, laptops, personal digital assistants (PDAs), satellite radios, GPS devices, multimedia devices, video devices, digital audio players (e.g., MP3 players), cameras, game consoles, tablets, smart devices, wearable devices, vehicles, meters, air pumps, large or small kitchen appliances, healthcare devices, implants, sensors / actuators, displays, or any other device with similar functionality. Some of the devices in UE 104 may be referred to as IoT devices (e.g., parking timers, air pumps, toasters, vehicles, heart monitors, etc.). UE 104 may also be referred to as a station, mobile station, subscriber station, mobile unit, subscriber unit, wireless unit, remote unit, mobile device, wireless device, wireless communication device, remote device, mobile subscriber station, access terminal, mobile terminal, wireless terminal, remote terminal, handheld device, user agent, mobile client, client, or some other appropriate terminology.

[0031] Although this disclosure may refer to 5G NR, it is applicable to other similar fields, such as LTE, LTE-Advanced (LTE-A), Code Division Multiple Access (CDMA), Global System for Mobile communications (GSM), or other radio / wireless access technologies.

[0032] Figure 2This is a block diagram of base station 210 communicating with UE 250 in the access network. In the DL, IP packets from EPC 160 can be provided to controller / processor 275. Controller / processor 275 implements Layer 3 and Layer 2 functions. Layer 3 includes the radio resource control (RRC) layer, and Layer 2 includes the packet data convergence protocol (PDCP) layer, radio link control (RLC) layer, and medium access control (MAC) layer. The controller / processor 275 provides: RRC layer functions associated with system information (e.g., Master Information Block (MIB), System Information Block (SIB)) broadcasting, RRC connection control (e.g., RRC connection paging, RRC connection establishment, RRC connection modification, and RRC connection release), mobility between radio access technologies (RATs), and measurement configuration for UE measurement reporting; PDCP layer functions associated with header compression / decompression, security (encryption, decryption, integrity protection, integrity verification), and handover support functions; RLC layer functions associated with upper-layer packet data unit (PDU) transmission, error correction via ARQ, concatenation, segmentation, and reassembly of RLC service data units (SDUs), resegmentation of RLC data PDUs, and reordering of RLC data PDUs; and mapping between logical channels and transport channels, multiplexing of MAC SDUs to transport blocks (TBs), and demultiplexing of MAC SDUs from TBs. SDU, scheduling information reporting, error correction via HARQ, priority processing, and MAC layer functions associated with logical channel priority ordering.

[0033] The transmit (TX) processor 216 and receive (RX) processor 270 implement Layer 1 functions associated with various signal processing functions. Layer 1 includes a physical (PHY) layer, which may include error detection on the transport channel, forward error correction (FEC) encoding / decoding of the transport channel, interleaving, rate matching, mapping to the physical channel, modulation / demodulation of the physical channel, and MIMO antenna processing. The TX processor 216 processes the mapping to the signal constellation diagram based on various modulation schemes (e.g., binary phase-shift keying (BPSK), quadrature phase-shift keying (QPSK), M-phase-shift keying (M-PSK), and M-quadrature amplitude modulation (M-QAM)). The encoded, decoded, and modulated symbols can then be split into parallel streams. Each stream can then be mapped to an OFDM subcarrier, multiplexed with a reference signal (e.g., a pilot) in the time and / or frequency domains, and then combined using an Inverse Fast Fourier Transform (IFFT) to generate a physical channel carrying a stream of time-domain OFDM symbols. This OFDM stream is spatially pre-coded to generate multiple spatial streams. Channel estimates from channel estimator 274 can be used to determine the coding and modulation schemes, as well as for spatial processing. These channel estimates can be derived from reference signals transmitted by UE 250 and / or channel condition feedback. Each spatial stream can then be provided to different antennas 220 via a separate transmitter 218TX. Each transmitter 218TX can modulate an RF carrier with the corresponding spatial stream for transmission.

[0034] At UE 250, each receiver 254RX receives signals via its corresponding antenna 252. Each receiver 254RX recovers the information modulated onto the RF carrier and provides this information to the RX processor 256. The TX processor 268 and RX processor 256 implement Layer 1 functions associated with various signal processing functions. The RX processor 256 can perform spatial processing on this information to recover any spatial streams destined for UE 250. If multiple spatial streams are destined for UE 250, they can be merged into a single OFDM symbol stream by the RX processor 256. The RX processor 256 then uses a Fast Fourier Transform (FFT) to transform the OFDM symbol stream from the time domain to the frequency domain. This frequency domain signal includes a separate OFDM symbol stream for each subcarrier of the OFDM signal. By determining the most probable signal constellation points transmitted by base station 210, the symbols on each subcarrier and the reference signal are recovered and demodulated. These soft decisions can be based on channel estimates calculated by channel estimator 258. These soft decisions are then decoded and deinterleaved to recover the data and control signals originally transmitted by base station 210 on the physical channel. These data and control signals are then provided to controller / processor 259, which implements Layer 3 and Layer 2 functions.

[0035] Controller / processor 259 may be associated with memory 260, which stores program code and data. Memory 260 may be referred to as computer-readable medium. In UL, controller / processor 259 provides demultiplexing, packet reassembly, decryption, header decompression, and control signal processing between transport and logical channels to recover IP packets from EPC 160. Controller / processor 259 is also responsible for error detection using ACK and / or NACK protocols to support HARQ operation.

[0036] Similar to the functions described in the DL transmission combined with base station 210, controller / processor 259 provides: RRC layer functions associated with system information (e.g., MIB, SIB) acquisition, RRC connection, and measurement reporting; PDCP layer functions associated with header compression / decompression and security (encryption, decryption, integrity protection, integrity verification); RLC layer functions associated with upper-layer PDU transmission, error correction via ARQ, concatenation, segmentation and reassembly of RLC SDUs, resegmentation of RLC data PDUs, and reordering of RLC data PDUs; and MAC layer functions associated with mapping between logical channels and transport channels, multiplexing of MAC SDUs onto TBs, demultiplexing of MAC SDUs from TBs, scheduling information reporting, error correction via HARQ, priority processing, and logical channel priority ordering.

[0037] The channel estimate derived by channel estimator 258 based on the reference signal or feedback transmitted by base station 210 can be used by TX processor 268 to select appropriate encoding / decoding and modulation schemes and facilitate spatial processing. The spatial stream generated by TX processor 268 can be provided to different antennas 252 via individual transmitters 254TX. Each transmitter 254TX can modulate an RF carrier with the corresponding spatial stream for transmission. This UL transmission is processed at base station 210 in a manner similar to that described in conjunction with the receiver function at UE 250. Each receiver 218RX receives a signal through its corresponding antenna 220. Each receiver 218RX recovers the information modulated onto the RF carrier and provides this information to RX processor 270.

[0038] Controller / processor 275 may be associated with memory 276, which stores program code and data. Memory 276 may be referred to as computer-readable medium. In the UL, controller / processor 275 provides demultiplexing, packet reassembly, decryption, header decompression, and control signal processing between transport and logical channels to recover IP packets from UE 250. IP packets from controller / processor 275 may be provided to EPC 160. Controller / processor 275 is also responsible for error detection using ACK and / or NACK protocols to support HARQ operation.

[0039] NR can refer to a radio configured to operate under a new air interface (e.g., an air interface other than one based on Orthogonal Frequency Divisional Multiple Access (OFDMA)) or a fixed transport layer (e.g., a transport layer other than IP). NR can utilize OFDM with a cyclic prefix (CP) on both the uplink and downlink, and may include support for half-duplex operation using time division duplexing (TDD). NR can include enhanced mobile broadband (eMBB) services with wide bandwidths (e.g., above 80 MHz), millimeter wave (mmW) services with high carrier frequencies (e.g., 60 GHz), massive machine-type communications (mMTC) for non-backward-compatible MTC technologies, and / or mission-critical communications for ultra-reliable low latency communications (URLLC) services.

[0040] It supports a single-component carrier bandwidth of 100 MHz. In one example, an NR resource block (RB) can span 12 subcarriers with a subcarrier bandwidth of 60 kHz over a duration of 0.25 ms, or 12 subcarriers with a bandwidth of 30 kHz over a duration of 0.5 ms (similarly, a bandwidth of 50 MHz for a 15 kHz sub-carrier spacing (SCS) over a duration of 1 ms). Each radio frame can consist of 10 subframes (10, 20, 40, or 80 NR slots) of 10 ms in length. Each slot can indicate the link direction (i.e., DL or UL) for data transmission, and the link direction of each slot can be dynamically switched. Each slot can include DL / UL data and DL / UL control data.

[0041] An NR RAN may include a central unit (CU) and a distributed unit (DU). An NR BS (e.g., gNB, 5G Node B, Node B, TRP, AP) may correspond to one or more BSs. NR cells may be configured as access cells (ACells) or data-only cells (DCells). For example, the RAN (e.g., a central unit or a distributed unit) may configure these cells. A DCell may be a cell used for carrier aggregation or dual connectivity and may not be used for initial access, cell selection / reselection, or handover. In some cases, a DCell may not transmit a synchronization signal (SS); in others, it may transmit an SS. An NR BS may transmit a downlink signal indicating the cell type to the UE. Based on this cell type indication, the UE may communicate with the NR BS. For example, the UE may determine which NR BS to consider for cell selection, access, handover, and / or measurement based on the indicated cell type.

[0042] Figure 3An example logical architecture of a distributed RAN 300 according to various aspects of this disclosure is shown. A 5G access node 306 may include an access node controller (ANC) 302. This ANC may be the CU of the distributed RAN. The backhaul interface to the next-generation core network (NG-CN) 304 may terminate at this ANC. The backhaul interface to the adjacent next-generation access node (NG-AN) 310 may terminate at this ANC. This ANC may include one or more TRPs 308 (which may also be referred to as BS, NR BS, Node B, 5G NB, AP, or certain other terms). As mentioned above, TRP can be used interchangeably with "cell".

[0043] TRP 308 may be a DU. These TRPs may connect to one ANC (ANC 302) or more ANCs (not shown). For example, for RAN sharing, radio as a service (RaaS), and service-specific ANC deployments, TRPs may connect to more than one ANC. TRPs may include one or more antenna ports. These TRPs may be configured to provide services to the UE individually (e.g., dynamically selected) or jointly (e.g., jointly transmitted).

[0044] The local architecture of the distributed RAN 300 can be used to illustrate the definition of fronthaul. An architecture supporting fronthaul solutions across different deployment types can be defined. For example, the architecture can be based on transmit network capabilities (e.g., bandwidth, latency, and / or jitter). The architecture can share features and / or components with LTE. Depending on various aspects, the NG-AN 310 can support dual connectivity with NR. The NG-AN can share a common fronthaul for LTE and NR.

[0045] This architecture enables collaboration between and within TRPs 308. For example, collaboration can be preset within a single TRP and / or across multiple TRPs via ANC 302. Depending on the circumstances, inter-TRP interfaces may be unnecessary or nonexistent.

[0046] Depending on various factors, the distributed RAN 300 architecture allows for dynamic configuration of split logical functions. PDCP, RLC, and MAC protocols can be adaptively placed at the ANC or the TRP.

[0047] Figure 4An example physical architecture of a distributed RAN 400 according to various aspects of this disclosure is shown. A centralized core network unit (C-CU) 402 can carry core network functions. This C-CU can be centrally deployed. The functions of the C-CU can be offloaded (e.g., offloaded to advanced wireless services (AWS)) to handle peak capacity. A centralized RAN unit (C-RU) 404 can carry one or more ANC functions. Optionally, the C-RU can carry core network functions locally. The C-RU can be deployed in a distributed manner. The C-RU can be located closer to the network edge. A DU 406 can carry one or more TRPs. This DU can be located at the network edge and has radio frequency (RF) functions.

[0048] Figure 5 This is a schematic diagram 500 illustrating communication between UE 504, a regular PLMN 510, and a disaster recovery PLMN 520. UE 504 is connected to base station 502 under normal operation and is initially registered to the regular PLMN 510, which can be either UE 504's home PLMN (HPLMN) or visited PLMN (VPLMN). The regular PLMN 510 provides standard cellular services to UE 504 under normal conditions via base station 502. The disaster recovery PLMN 520 operates base station 512, which is adjacent to base station 502. Under normal conditions, the disaster recovery PLMN 520 can be a prohibited PLMN for UE 504. UE 504 may have the same structure and components as UE 250. Base stations 502 and 512 may each have the same structure and components as base station 210.

[0049] Disaster roaming is a feature specified in the 3GPP standard that allows users to access other mobile networks (such as a disaster-use PLMN 520) during disasters or emergencies, even if their home networks (such as a regular PLMN 510) are unavailable. This feature enables users to access voice and data services on alternative networks when their home network is interrupted due to a disaster. The regular PLMN 510 can broadcast disaster roaming information in the system information block (SIB) 550 via base station 502.

[0050] When a regular PLMN 510 encounters a disaster, UE 504 may attempt to register with the disaster-using PLMN 520 to obtain disaster roaming services. UE 504 sends a registration request message 530 to the disaster-using PLMN 520 via base station 512. The registration request message 530 indicates that UE 504 is requesting registration for disaster roaming services for the identified PLMN experiencing the disaster.

[0051] The PLMN 520 used for disaster recovery includes a core network 522, which may include an AMF for 5G systems, an MME for 4G systems, or similar network functions for 6G systems. When the core network 522 receives a registration request message 530, it assesses whether it can provide disaster recovery roaming services to UE 504. The core network 522 may determine that it cannot support providing disaster recovery roaming services to UE 504 for several reasons.

[0052] When the core network 522 determines that it cannot provide disaster roaming service, it sends a NAS rejection message 540 to the UE 504 via base station 512. The NAS rejection message 540 can be an ATTACH REJECT message in 4G systems, a REGISTRATION REJECT message, a TRACKING AREAUPDATE REJECT message, or a SERVICE REJECT message in 5G and 6G systems. The rejection message 540 includes a reason value indicating why the disaster roaming request is rejected. In 5G systems, this reason value is defined as 5G mobility management (5GMM) reason #80, which indicates "disaster roaming is not permitted for the identified PLMN with a disaster condition." For 4G and 6G systems, similar reason values ​​exist or will be defined to indicate that disaster roaming is not permitted.

[0053] A synchronization problem arises when UE 504 receives a NAS rejection message 540 with a reason value indicating that disaster roaming is not permitted. Under normal operation, when UE 504 receives such a rejection message, UE 504 immediately performs a local release of the NAS signaling connection 570 without initiating a protection timer. A protection timer is a timer mechanism that allows UE 504 to wait for the network to properly release the connection before UE 504 transitions to an idle state. Without this protection timer, UE 504 immediately releases the connection locally and enters an idle state.

[0054] The lack of a protection timer can cause synchronization issues between UE 504 and core network 522. When UE 504 performs an immediate local release of NAS signaling connection 570, UE 504 considers the connection terminated and enters an idle state. However, core network 522 may still maintain the connection on its side because it has not yet started or completed its connection release procedure. This results in an asynchronous state where UE 504 believes the connection has been released, while core network 522 still believes the connection is active. This asynchronous state can lead to communication failures, resource management problems, and potential conflicts when UE 504 attempts subsequent network operations while the network still maintains resources for the connection it considers active.

[0055] This synchronization issue affects multiple generations of cellular systems, including the 4G Evolved Packet System (EPS), 5G System (5GS), and the future 6G System (6GS). In each system, when a NAS message requesting disaster roaming is rejected for a reason indicating that disaster roaming is not permitted for a defined PLMN with a disaster condition, UE 504 fails to initiate an appropriate protection timer. Without this timer, UE 504 cannot maintain proper synchronization of its connection state with the network during disaster roaming scenarios.

[0056] This disclosure discloses a procedure for managing connection release after disaster roaming is denied. The procedure involves UE 504 and the core network 522 of the disaster-using PLMN 520. When UE 504 receives a NAS rejection message 540 from the core network 522 of the disaster-using PLMN 520 containing a reason value indicating that disaster roaming is not permitted, UE 504 encounters a synchronization problem under normal operation. Specifically, UE 504 immediately performs a local release of the NAS signaling connection 570 without starting a protection timer, resulting in an asynchronous state where UE 504 believes the connection has been released, while the core network 522 may still keep the connection active.

[0057] To address this synchronization issue, this disclosure proposes a technique in which UE 504 initiates a protection timer 580 upon receiving a NAS rejection message 540 containing a reason indicating that disaster roaming is not permitted for a determined PLMN with a disaster condition. The specific timer initiated depends on the generation of the communication system. In 5GS, UE 504 initiates the timer. In 4GEPS, UE 504 starts the timer. In future 6GS, UE 504 will start another designated timer for managing the release of signaling connections.

[0058] The protection timer 580 provides a predetermined duration, such as 10 seconds, during which UE 504 waits for core network 522 to release the signaling connection. This waiting period allows core network 522 to complete its internal procedures and may send a connection release command 590 to UE 504. Network behavior during this period is not guaranteed, as core network 522 may or may not initiate the connection release within the timer's duration.

[0059] Based on network actions, this procedure produces one of two results. If the core network 522 sends a connection release command 590 to the UE 504 before the protection timer 580 expires, the UE 504 stops the protection timer 580 and continues the release of the NAS signaling connection 570 as instructed by the network. The UE 504 and the core network 522 then synchronously transition to an idle state. Alternatively, if the protection timer 580 expires without receiving a connection release command 590 from the core network 522, the UE 504 performs a local release of the NAS signaling connection 570. This fallback mechanism prevents the UE 504 from waiting indefinitely for a network response and helps conserve battery power while allowing the UE 504 to transition to an idle state.

[0060] The triggering NAS rejection message 540 can be of various types, depending on the system and the rejected procedure. In 4G systems, this message can be an attach rejection message. In 5G and 6G systems, this message can be a registration rejection message. Furthermore, in these systems, this message can be a tracking area update rejection message or a service rejection message. The reason value that triggers the protection timer 580 in these messages is 5G Mobility Management (5GMM) reason #80 in 5G systems, indicating "disaster roaming is not permitted for the identified PLMN with a disaster condition". For 4G systems, the equivalent Evolved Packet System Mobility Management (EMM) reason value related to disallowing disaster roaming will trigger the timer. Similarly, for 6G systems, the corresponding 6G Mobility Management (6GMM) reason value indicating disallowing disaster roaming will start the timer. .

[0061] This solution is generally applicable to multiple generations of mobile communication technologies. The reason value indicating that disaster roaming is not allowed can originate from core network 522, whether it operates as a 4G core network with MME, a 5G core network with AMF, or a 6G core network with equivalent mobility management functions. By implementing this protection timer mechanism, this method maintains synchronization between UE 504 and core network 522 during disaster roaming denial scenarios, preventing communication failures and resource management conflicts that would otherwise occur due to asynchronous connection states.

[0062] As mentioned above, when a 5G UE receives a NAS rejection message with certain 5GMM reason values, the UE starts a timer. This is to allow the network to release the N1 NAS signaling connection. The list of reason values ​​includes reason #80, which indicates "Disaster roaming is not permitted for the identified PLMN with a disaster condition." Figure 5 In the example, when UE 504 receives a NAS rejection message 540 containing 5GMM reason #80 from the core network 522 of the PLMN 520 used for disaster recovery, UE 504 starts a protection timer 580, specifically a timer... This timer mechanism prevents the immediate local release of the NAS signaling connection 570 and maintains synchronization between UE 504 and core network 522.

[0063] Similarly, this protection timer principle can be extended to other generations of cellular technology. For 4G systems, when UE 504 receives an ATTACH REJECT, TRACKING AREA UPDATE REJECT, or SERVICE REJECT message with an EMM cause value indicating that catastrophic roaming is not permitted, UE 504 will start a timer. The proposed mechanism applies to any EMM reason that indicates a PLMN with a defined disaster condition is not permitted to conduct disaster roaming.

[0064] For 6G systems, this disclosure proposes the introduction of a new protection timer that serves the same synchronization function. When UE 504 receives a Registration Reject message or other NAS Reject message 540 with a 6GMM reason value indicating that disaster roaming is not permitted, UE 504 will start this timer. This mechanism applies to any 6GMM reason corresponding to the refusal to provide disaster roaming services to the determined PLMN 510 in the event of a disaster.

[0065] This protection timer mechanism provides a consistent approach to handling catastrophic roaming denials across multiple generations of common applications. Regardless of whether the core network 522 operates as a 4G core network with an MME, a 5G core network with an AMF, or a 6G core network with equivalent mobility management capabilities, the UE 504 will initiate an appropriate protection timer upon receiving a catastrophic roaming denial. This prevents synchronization issues that would otherwise occur if the UE 504 immediately performs a local release of the NAS signaling connection 570 without waiting for the core network 522 to complete its connection release procedure. The protection timer 580 provides the core network 522 with a predetermined duration, typically approximately 10 seconds, to send a connection release command 590 before the UE 504 performs a local release when the timer expires.

[0066] Figure 6 This is a flowchart 600 of a method for managing connection release after disaster roaming is denied. This method can be performed by a UE (e.g., UE 504). In operation 602, the UE sends a NAS request message to the core network of the PLMN used in the disaster, requesting disaster roaming service for the identified PLMN with the disaster status. In some implementations, the NAS request message is one of the following: a registration request message; an attach request message; a tracking area update request message; or a service request message.

[0067] In operation 604, the UE receives a NAS rejection message from the core network. This NAS rejection message includes a reason value indicating that disaster roaming is not permitted for the identified PLMN with the disaster condition. In some implementations, the NAS rejection message is one of the following: an attach rejection message; a registration rejection message; a tracking area update rejection message; or a service rejection message. In some implementations, when the UE is operating in 5GS, the reason value is 5GMM reason #80. In some implementations, when the UE is operating in 4G EPS, the reason value is an EMM reason indicating that disaster roaming is not permitted. In some implementations, when the UE is operating in 6GS, the reason value is a 6GMM reason indicating that disaster roaming is not permitted.

[0068] In operation 606, the UE initiates a protection timer in response to receiving the NAS rejection message with the cause value. This protection timer provides the core network with a predetermined duration for releasing the NAS signaling connection. In some implementations, when the UE is operating in 5GS, the protection timer is a timer... In some implementations, when the UE is running in 4G EPS, the protection timer is a timer. In some implementations, when the UE is running in 6GS, the protection timer is a 6G-specific timer.

[0069] In operation 608, if no connection release command is received from the core network before the protection timer expires, the UE performs a local release of the NAS signaling connection upon the expiration of the protection timer. In some embodiments, to perform the local release of the NAS signaling connection upon the expiration of the protection timer, the UE performs at least one of the following: releasing NAS signaling connection resources, releasing access stratum resources, and entering the corresponding idle mobility management state. In some embodiments, the method further includes transitioning to an idle state after performing the local release of the NAS signaling connection.

[0070] In operation 610, when the UE receives the connection release command from the core network before the protection timer expires, the UE stops the protection timer and releases the NAS signaling connection.

[0071] UE 504 and execution Figure 6 The method can be used by the UE with Figure 2 The hardware components of the UE 250 shown are implemented using similar hardware components. This hardware may include one or more antennas 252, a receiver (RX) 254RX, a transmitter (TX) 254TX, a receive processor 256, a transmit processor 268, a controller / processor 259, and a memory 260. The antennas 252, receiver 254RX, and transmitter 254TX are configured to receive radio signals from and transmit radio signals to a base station (e.g., base station 512). The RX processor 256 and TX processor 268 are configured to process these signals at the physical layer, while the controller / processor 259 handles higher-layer functions, including NAS signaling.

[0072] In the context of this disclosure, controller / processor 259 executes instructions stored in memory 260, specifically configured to manage the connection release process following a disaster roaming rejection. Controller / processor 259 instructs the sending of a NAS request message (e.g., a registration request) for the disaster roaming service. Upon receiving a NAS rejection message (e.g., a registration rejection) via the receive link, controller / processor 259 parses the message to identify a reason value indicating that disaster roaming is not permitted (e.g., 5GMM reason #80). In response, controller / processor 259 starts a protection timer (e.g., a timer in 5GS). 4G EPS (or the corresponding timer in the 6GS). The controller / processor 259 then monitors for connection release commands from the network. If no such command is received before the timer expires, the controller / processor 259 initiates a local release of the NAS signaling connection to maintain synchronization and conserve power, such as... Figure 6The method described therein.

[0073] It should be understood that the specific order or hierarchy of the program blocks in the disclosed program / flowcharts is an illustration of an exemplary method. Based on design preferences, it should be understood that the specific order or hierarchy of the program blocks in these program / flowcharts may be rearranged. Furthermore, certain program blocks may be combined or omitted. The appended method claims present the elements of the program blocks in an exemplary order and are not intended to be limited to the specific order or hierarchy presented.

[0074] The foregoing description is provided to enable any person skilled in the art to practice the various aspects described herein. Various modifications to these aspects will be apparent to those skilled in the art, and the general principles defined herein may be applied to other aspects. Therefore, the claims are not intended to be limited to the aspects shown herein, but should be given the full scope consistent with the language of the claims, wherein a reference to an element in the singular is not intended to mean “one and only one”, but rather “one or more” unless expressly stated otherwise. The word “exemplary” as used herein means “serving as an example, instance, or illustration.” Any aspect described herein as “exemplary” is not necessarily to be construed as being more preferred or advantageous than other aspects. Unless expressly stated otherwise, the term “some” means one or more. Combinations such as “at least one of A, B, or C,” “one or more of A, B, or C,” “at least one of A, B, and C,” “one or more of A, B, and C,” and “A, B, C, or any combination thereof” include any combination of A, B, and / or C, and may include multiple A, multiple B, or multiple C. Specifically, combinations such as "at least one of A, B, or C", "one or more of A, B, or C", "at least one of A, B, and C", "one or more of A, B, and C", and "A, B, C, or any combination thereof" can be A only, B only, C only, A and B, A and C, B and C, or A and B and C, wherein any such combination may include one or more members of A, B, or C. All structural and functional equivalents of elements throughout the various aspects described in this disclosure, whether known to those skilled in the art or to be known hereafter, are expressly incorporated herein by reference and are intended to be covered by the claims. Furthermore, nothing disclosed herein is intended to be offered to the public, whether or not such disclosure is expressly stated in the claims. The terms "module," "mechanism," "element," "device," etc., are not interchangeable with the term "means." Therefore, unless an element is expressly stated using the phrase "means for…", no claim element should be construed as means plus function.

Claims

1. A wireless communication method for a user equipment, comprising: Send a non-access stratum request message to the core network of the public land mobile network used in the disaster, the non-access stratum request message requesting disaster roaming service for the identified public land mobile network with disaster status. The core network receives a non-access stratum rejection message, which includes a reason value indicating that disaster roaming is not permitted for the identified public terrestrial mobile network with the disaster condition. A protection timer is started in response to receiving the non-access stratum rejection message with the cause value, wherein the protection timer provides the core network with a predetermined duration for releasing the non-access stratum signaling connection; If no connection release command is received from the core network before the protection timer expires, the local release of the non-access stratum signaling connection is performed when the protection timer expires; and When a connection release command is received from the core network before the protection timer expires, the protection timer is stopped and the non-access stratum signaling connection is released.

2. The method of claim 1, wherein when the user equipment is operating in a fifth-generation system, the protection timer is a timer. .

3. The method of claim 1, wherein when the user equipment is operating in a fourth-generation evolved packet system, the protection timer is a timer. .

4. The method of claim 1, wherein when the user equipment is operating in a sixth-generation system, the protection timer is a sixth-generation dedicated timer.

5. The method of claim 1, wherein the non-access stratum request message is one of the following: Registration request message; Attach request message; Tracking area update request message; or Business request message.

6. The method of claim 1, wherein the non-access stratum rejection message is one of the following: Attach a rejection message; Registration rejection message; The tracking area updates the rejection message; or Business rejection message.

7. The method of claim 1, wherein when the user equipment is operating in a fifth-generation system, the reason value is fifth-generation mobility management reason #80.

8. The method of claim 1, wherein when the user equipment is operating in a fourth generation evolved packet system, the cause value is an evolved packet system mobility management cause that indicates that disaster roaming is not permitted.

9. The method of claim 1, wherein when the user equipment is operating in a sixth-generation system, the cause value is a sixth-generation mobility management cause indicating that disaster roaming is not permitted.

10. The method of claim 1, further comprising: After the local release of the non-access stratum signaling connection is executed, it transitions to an idle state.

11. The method of claim 1, wherein performing the local release of the non-access stratum signaling connection upon the expiration of the protection timer comprises at least one of the following: Release non-access stratum signaling connection resources; Release access layer resources; and Enter the corresponding idle mobility management state.

12. A device for wireless communication, the device being a user equipment, comprising: Memory; as well as At least one processor, coupled to the memory and configured to: Send a non-access stratum request message to the core network of the public land mobile network used in the disaster, the non-access stratum request message requesting disaster roaming service for the identified public land mobile network with disaster status. The core network receives a non-access stratum rejection message, which includes a reason value indicating that disaster roaming is not permitted for the identified public terrestrial mobile network with the disaster condition. A protection timer is started in response to receiving the non-access stratum rejection message with the cause value, wherein the protection timer provides the core network with a predetermined duration for releasing the non-access stratum signaling connection; If no connection release command is received from the core network before the protection timer expires, the local release of the non-access stratum signaling connection is performed when the protection timer expires; and When a connection release command is received from the core network before the protection timer expires, the protection timer is stopped and the non-access stratum signaling connection is released.

13. The device of claim 12, wherein when the user equipment is operating in a fifth-generation system, the protection timer is a timer. .

14. The device of claim 12, wherein when the user equipment is operating in a fourth-generation evolved packet system, the protection timer is a timer. .

15. The device of claim 12, wherein when the user equipment is operating in a sixth-generation system, the protection timer is a sixth-generation dedicated timer.

16. The device of claim 12, wherein the non-access stratum request message is one of the following: Registration request message; Attach request message; Tracking area update request message; or Business request message.

17. The device of claim 12, wherein the non-access stratum rejection message is one of the following: Attach a rejection message; Registration rejection message; The tracking area updates the rejection message; or Business rejection message.

18. The device of claim 12, wherein when the user equipment is operating in a fifth-generation system, the cause value is fifth-generation mobility management cause #80.

19. The device of claim 12, wherein when the user equipment is operating in a fourth generation evolved packet system, the cause value is an evolved packet system mobility management cause that indicates that disaster roaming is not permitted.

20. A computer-readable medium storing computer-executable code for wireless communication of a user equipment, including code for performing the following operations: Send a non-access stratum request message to the core network of the public land mobile network used in the disaster, the non-access stratum request message requesting disaster roaming service for the identified public land mobile network with disaster status. The core network receives a non-access stratum rejection message, which includes a reason value indicating that disaster roaming is not permitted for the identified public terrestrial mobile network with the disaster condition. A protection timer is started in response to receiving the non-access stratum rejection message with the cause value, wherein the protection timer provides the core network with a predetermined duration for releasing the non-access stratum signaling connection; If no connection release command is received from the core network before the protection timer expires, the local release of the non-access stratum signaling connection is performed when the protection timer expires; and When a connection release command is received from the core network before the protection timer expires, the protection timer is stopped and the non-access stratum signaling connection is released.

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