Mobile device and method for achieving end-to-end reliability and improving fault tolerance in wireless systems

Abstract

A wireless transmit / receive unit (WTRU) may transmit a request message to establish or modify a protocol data unit (PDU) session with a network. In one example, the request message may indicate that the PDU session is an alternative PDU session. In addition, the WTRU may receive indication information from a network indicating that the PDU session is an alternative PDU session. In addition, the WTRU may determine whether the PDU session is in a discarded state based on the received indication information. Further, the WTRU may transmit uplink data associated with the PDU session based on a determination that the PDU session is no longer in the discarded state. In another example, a determination that a PDU session is no longer in a discard state may be based on indication information in an attention (AT) command. In addition, indication information in the AT command may be received from the application.

Description

[0001] Cross - Reference to Related Applications

[0002] This application claims the benefit of U.S. Provisional Application No. 63 / 422,255, filed on November 3, 2022, the content of which is incorporated herein by reference. Background Art

[0003] To support wireless services such as ultra - reliable low - latency communication (URLLC), a wireless transmit / receive unit (WTRU) may establish two redundant protocol data unit (PDU) sessions over a fifth - generation (5G) network such that the 5G system (5GS) establishes the user - plane paths of the two redundant PDU sessions as separate. In this case, the user's subscription indicates whether the user is allowed to have redundant PDU sessions, and this indication is provided from the Unified Data Management (UDM) to the Session Management Function (SMF). The Next Generation Radio Access Network (NG - RAN) may utilize two NG - RAN nodes (e.g., a primary NG - RAN and a secondary NG - RAN), or a single NG - RAN node to implement redundant user - plane resources for the two PDU sessions. In both cases, there is a single N1 interface for the Access and Mobility Management Function (AMF).

[0004] The 5GS also supports redundant transmission on the N3 / N9 interfaces, where two redundant N3 / N9 tunnels with independent user - plane paths are established between the User - Plane Function (UPF) and the NG - RAN to transmit replicated user packets. This redundant transmission using two N3 / N9 tunnels is performed at the Quality of Service (QoS) flow granularity that shares the same QoS flow identifier (ID). In this case, these packets may be transmitted via two N3 tunnels between a single UPF and the NG - RAN, respectively. It is assumed that the NG - RAN node and the PDU session anchor (PSA) UPF will support packet replication and elimination functions. Summary of the Invention

[0005] A wireless transmit / receive unit (WTRU) may transmit a request message to establish or modify a protocol data unit (PDU) session with a network. In one example, the request message indicates that the PDU session is an alternative PDU session. Additionally, the WTRU may receive indication information from the network indicating that the PDU session is an alternative PDU session. Additionally, the WTRU may determine whether the PDU session is in a discarded state based on the received indication information. Additionally, based on the determination that the PDU session is no longer in a discarded state, the WTRU may transmit uplink data associated with the PDU session.

[0006] In another example, the determination that the PDU session is no longer in the discarded state may be based on indication information in an Attention (AT) command. Additionally, the indication information in the AT command may be received from an application. In one example, the application may be hosted in a WTRU. In another example, the application may be hosted in the network.

[0007] In another example, the WTRU may receive, in a PDU session establishment acceptance message, indication information indicating that the PDU session is an alternative PDU session. In another example, the WTRU may receive, in a PDU session modification command message, indication information indicating that the PDU session is an alternative PDU session.

[0008] In yet another example, the WTRU may determine that the PDU session is in the discarded state based on the indication information in the PDU session establishment acceptance message. In another example, the WTRU may determine that the PDU session is in the discarded state based on the indication information in the PDU session modification command message.

[0009] Additionally, the WTRU may determine that the PDU session is no longer in the discarded state based on receiving downlink data. In one example, the downlink data may be associated with the PDU session. In another example, the downlink data may be Ultra-Reliable Low-Latency Communication (URLLC). BRIEF DESCRIPTION OF THE DRAWINGS

[0010] A more detailed understanding may be obtained from the following description given by way of example in conjunction with the accompanying drawings, in which like reference numerals in the drawings denote like elements, and in which:

[0011] Figure 1A is a system diagram showing an example communication system in which one or more disclosed embodiments may be implemented;

[0012] Figure 1B is a system diagram showing an example Wireless Transmit / Receive Unit (WTRU) that may be used in the Figure 1A shown communication system according to one embodiment;

[0013] Figure 1C is a system diagram showing an example Radio Access Network (RAN) and an example Core Network (CN) that may be used in the Figure 1A shown communication system according to one embodiment;

[0014] Figure 1D is a system diagram showing another example RAN and another example CN that may be used in the Figure 1A shown communication system according to one embodiment;

[0015] Figure 2is a system diagram showing an example WTRU that interacts with a terminal device (TE) and a mobile terminal (MT) via an attention (AT) command;

[0016] Figure 3 is a diagram showing an example of alternative protocol data unit (PDU) session establishment and state change;

[0017] Figure 4 is a system diagram showing an example of a communication device with multiple mobile terminals in a system;

[0018] Figure 5 is a signaling diagram showing an example of an alternative PDU session initiated by a WTRU;

[0019] Figure 6 is a signaling diagram showing an example of a PDU session state change process initiated by a WTRU;

[0020] Figure 7 is a signaling diagram showing an example of an alternative PDU session initiated by an application server (AS);

[0021] Figure 8 is a flowchart showing an example of a WTRU that supports an alternative PDU session;

[0022] Figure 9 is a signaling diagram showing an example of a network-initiated PDU session state change process;

[0023] Figure 10 is a signaling diagram showing an example of a PDU session creation and state change process with network coordination; and

[0024] Figure 11 is a signaling diagram showing an example of a PDU session creation and state change process with WTRU coordination. Detailed Description

[0025] Figure 1AFIG. is a diagram illustrating an example communication system 100 in which one or more of the disclosed embodiments may be implemented. The communication system 100 may be a multi-access system that provides content such as voice, data, video, messaging, broadcast, etc. to a plurality of wireless users. The communication system 100 may enable the plurality of wireless users to access this content by sharing system resources including wireless bandwidth. For example, the communication system 100 may employ one or more channel access methods such as code division multiple access (CDMA), time division multiple access (TDMA), frequency division multiple access (FDMA), orthogonal FDMA (OFDMA), single carrier FDMA (SC-FDMA), zero-tail unique word discrete Fourier transform spread OFDM (ZT-UW-DFT-S-OFDM), unique word OFDM (UW-OFDM), resource block filtered OFDM, filter bank multicarrier (FBMC), etc.

[0026] As Figure 1A shown, the communication system 100 may include wireless transmit / receive units (WTRUs) 102a, 102b, 102c, 102d, a radio access network (RAN) 104, a core network (CN) 106, a public switched telephone network (PSTN) 108, the Internet 110, and other networks 112, but it should be understood that the disclosed embodiments contemplate any number of WTRUs, base stations, networks, and / or network elements. Each of the WTRUs 102a, 102b, 102c, 102d may be any type of device configured to operate and / or communicate in a wireless environment. By way of example, any one of the WTRUs 102a, 102b, 102c, 102d may be referred to as a station (STA), may be configured to transmit and / or receive wireless signals, and may include a user equipment (UE), a mobile station, a fixed or mobile subscriber unit, a subscription-based unit, a pager, a cellular phone, a personal digital assistant (PDA), a smartphone, a laptop computer, a netbook, a personal computer, a wireless sensor, a hotspot or Mi-Fi device, an Internet of Things (IoT) device, a watch or other wearable device, a head-mounted display (HMD), a vehicle, a drone, a medical device and application (e.g., remote surgery), an industrial device and application (e.g., a robot and / or other wireless devices operating in an industrial and / or automation processing chain environment), a consumer electronic device, a device operating on a commercial and / or industrial wireless network, etc. Any one of the WTRUs 102a, 102b, 102c, and 102d may be interchangeably referred to as a UE.

[0027] The communication system 100 may also include base station 114a and / or base station 114b. Each of base stations 114a, 114b may be any type of device configured to wirelessly interface with at least one of WTRUs 102a, 102b, 102c, 102d to facilitate access to one or more communication networks, such as CN 106, Internet 110, and / or other networks 112. By way of example, base stations 114a, 114b may be base transceiver stations (BTSs), Node Bs, eNode Bs (eNBs), home Node Bs, home eNode Bs, next-generation Node Bs (e.g., gNode Bs (gNBs)), New Radio (NR) Node Bs, site controllers, access points (APs), wireless routers, etc. Although base stations 114a, 114b are each depicted as a single element, it should be understood that base stations 114a, 114b may include any number of interconnected base stations and / or network elements.

[0028] Base station 114a may be part of RAN 104, which may also include other base stations and / or network elements (not shown), such as base station controllers (BSCs), radio network controllers (RNCs), relay nodes, etc. Base station 114a and / or base station 114b may be configured to transmit and / or receive wireless signals on one or more carrier frequencies, which may be referred to as cells (not shown). These frequencies may be in licensed spectrum, unlicensed spectrum, or a combination of licensed and unlicensed spectrum. A cell may provide coverage of wireless services to a particular geographic area, which may be relatively fixed or may change over time. The cell may also be divided into cell sectors. For example, the cell associated with base station 114a may be divided into three sectors. Thus, in one embodiment, base station 114a may include three transceivers, i.e., one transceiver for each sector of the cell. In one embodiment, base station 114a may employ multiple-input multiple-output (MIMO) technology and may use multiple transceivers for each sector of the cell. For example, beamforming may be used to transmit and / or receive signals in a desired spatial direction.

[0029] Base stations 114a, 114b may communicate with one or more of WTRUs 102a, 102b, 102c, 102d via air interface 116, which may be any suitable wireless communication link (e.g., radio frequency (RF), microwave, centimeter wave, millimeter wave, infrared (IR), ultraviolet (UV), visible light, etc.). Any suitable radio access technology (RAT) may be used to establish air interface 116.

[0030] More specifically, as described above, the communication system 100 can be a multi-access system and can employ one or more channel access schemes, such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA, etc. For example, the base stations 114a and the WTRUs 102a, 102b, 102c in the RAN 104 can implement radio technologies such as Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access (UTRA), which can use Wideband CDMA (WCDMA) to establish the air interface 116. WCDMA can include communication protocols such as High-Speed Packet Access (HSPA) and / or Evolved HSPA (HSPA+). HSPA can include High-Speed Downlink (DL) Packet Access (HSDPA) and / or High-Speed Uplink (UL) Packet Access (HSUPA).

[0031] In one embodiment, the base stations 114a and the WTRUs 102a, 102b, 102c can implement radio technologies such as Evolved UMTS Terrestrial Radio Access (E-UTRA), which can use Long-Term Evolution (LTE) and / or LTE-Advanced (LTE-A) and / or LTE-A Pro to establish the air interface 116.

[0032] In one embodiment, the base stations 114a and the WTRUs 102a, 102b, 102c can implement radio technologies such as NR radio access, which can use NR to establish the air interface 116.

[0033] In an embodiment, the base stations 114a and the WTRUs 102a, 102b, 102c can implement multiple radio access technologies. For example, the base stations 114a and the WTRUs 102a, 102b, 102c can implement LTE radio access and NR radio access together, such as using the Dual Connectivity (DC) principle. Thus, the air interface used by the WTRUs 102a, 102b, 102c can be characterized by multiple types of radio access technologies and / or transmissions to / from multiple types of base stations (e.g., eNBs and gNBs).

[0034] In other embodiments, the base station 114a and the WTRUs 102a, 102b, 102c may implement radio technologies such as Institute of Electrical and Electronics Engineers (IEEE) 802.11 (i.e., Wi-Fi), IEEE 802.16 (i.e., Worldwide Interoperability for Microwave Access (WiMAX)), CDMA2000, CDMA2000 1X, CDMA2000 EV-DO, Interim Standard 2000 (IS-2000), Interim Standard 95 (IS-95), Interim Standard 856 (IS-856), Global System for Mobile Communications (GSM), Enhanced Data Rates for GSM Evolution (EDGE), GSM EDGE (GERAN), and the like.

[0035] For example, Figure 1A the base station 114b in may be a wireless router, a home Node B, a home eNode B, or an access point, and may utilize any suitable RAT to facilitate wireless connectivity in a local area, such as a commercial venue, a home, a vehicle, a campus, an industrial facility, an air corridor (e.g., for drones), a road, etc. In one embodiment, the base station 114b and the WTRUs 102c, 102d may implement a radio technology such as IEEE 802.11 to establish a wireless local area network (WLAN). In one embodiment, the base station 114b and the WTRUs 102c, 102d may implement a radio technology such as IEEE 802.15 to establish a wireless personal area network (WPAN). In yet another embodiment, the base station 114b and the WTRUs 102c, 102d may utilize a cellular-based RAT (e.g., WCDMA, CDMA2000, GSM, LTE, LTE-A, LTE-A Pro, NR, etc.) to establish a pico cell or a femto cell. As Figure 1A shown, the base station 114b may be directly connected to the Internet 110. Thus, the base station 114b may not need to access the Internet 110 via the CN 106.

[0036] The RAN 104 may communicate with the CN 106, which may be any type of network configured to provide voice, data, applications, and / or voice over Internet Protocol (VoIP) services to one or more of the WTRUs 102a, 102b, 102c, 102d. The data may have different quality of service (QoS) requirements, such as different throughput requirements, latency requirements, fault tolerance requirements, reliability requirements, data throughput requirements, mobility requirements, etc. The CN 106 may provide call control, billing services, location-based services for mobile devices, prepaid calling, Internet connectivity, video distribution, etc. and / or perform advanced security functions, such as user authentication. Although in Figure 1AAlthough not shown, it should be understood that RAN 104 and / or CN 106 may communicate directly or indirectly with other RANs using the same RAT as RAN 104 or a different RAT. For example, in addition to being connected to RAN 104 which may utilize NR radio technology, CN 106 may also communicate with another RAN (not shown) using GSM, UMTS, CDMA 2000, WiMAX, E-UTRA, or WiFi radio technology.

[0037] CN 106 may also act as a gateway for WTRU 102a, 102b, 102c, 102d to access the PSTN 108, the Internet 110, and / or other networks 112. The PSTN 108 may include a circuit-switched telephone network that provides plain old telephone service (POTS). The Internet 110 may include a global system of interconnected computer networks and devices that use common communication protocols such as the Transmission Control Protocol (TCP), the User Datagram Protocol (UDP), and / or the Internet Protocol (IP) in the TCP / IP Internet protocol suite. The network 112 may include wired and / or wireless communication networks owned and / or operated by other service providers. For example, the network 112 may include another CN connected to one or more RANs, which may use the same RAT as RAN 104 or a different RAT.

[0038] Some or all of the WTRU 102a, 102b, 102c, 102d in the communication system 100 may include multi-mode capabilities (e.g., the WTRU 102a, 102b, 102c, 102d may include multiple transceivers for communicating with different wireless networks via different wireless links). For example, Figure 1A the WTRU 102c shown in may be configured to communicate with a base station 114a that may use a cellular-based radio technology and with a base station 114b that may use IEEE 802 radio technology.

[0039] The following abbreviations and acronyms may be used in the embodiments and examples herein:

[0040] 5GS 5G System

[0041] 5GC 5G Core

[0042] Alt. Alternative

[0043] AMF Access and Mobility Function

[0044] API Application Programming Interface

[0045] WTRU App WTRU Application

[0046] AS Application Server

[0047] AT Attention

[0048] CN Core Network

[0049] DL Downlink

[0050] DN Data Network

[0051] DNN Data Network Name

[0052] FRER Frame Replication and Elimination for Reliability

[0053] GTP GPRS Tunneling Protocol

[0054] GTP-U GPRS Tunneling Protocol for the User Plane

[0055] gNB gNodeB

[0056] ID Identifier

[0057] IP Internet Protocol

[0058] MT Mobile Terminal

[0059] NAS Non-Access Stratum

[0060] NAS-MM NAS – Mobility Management

[0061] NAS-SM NAS – Session Management

[0062] NEF Network Exposure Function

[0063] NG-RAN Next Generation Radio Access Network

[0064] NR New Radio

[0065] PCC Policy Charging and Control

[0066] PCF Policy Control Function

[0067] PDU Protocol Data Unit

[0068] PSA PDU Session Anchor

[0069] QoE Quality of Experience

[0070] QoS Quality of Service

[0071] RAN Radio Access Network

[0072] RFSP RAT / Frequency Selection Priority

[0073] RRC Radio Resource Control

[0074] RRM Radio Resource Management

[0075] RSD Routing Descriptor

[0076] SM Session Management

[0077] SMF Session Management Function

[0078] S-NSSAI Single Network Slice Selection Assistance Information

[0079] TSN Time-Sensitive Network

[0080] TE Terminal Equipment

[0081] UCU WTRU Configuration Update

[0082] UDM Unified Data Management

[0083] UDP User Datagram Protocol

[0084] WTRU User Equipment

[0085] UL Uplink

[0086] UPF User Plane Function

[0087] URLLC Ultra-Reliable and Low-Latency Communication

[0088] URSP WTRU Routing Selection Policy

[0089] Figure 1B is a system diagram showing an example WTRU 102. As Figure 1B shown, among other things, the WTRU 102 can include a processor 118, a transceiver 120, a transmit / receive element 122, a speaker / microphone 124, a keyboard 126, a display / touchpad 128, a non-removable memory 130, a removable memory 132, a power supply 134, a Global Positioning System (GPS) chipset 136, and / or other peripheral devices 138. It should be understood that the WTRU 102 can include any sub-combination of the foregoing elements while remaining consistent with the embodiments.

[0090] The processor 118 can be a general-purpose processor, a dedicated processor, a conventional processor, a digital signal processor (DSP), multiple microprocessors, one or more microprocessors associated with a DSP core, a controller, a microcontroller, an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), any other type of integrated circuit (IC), a state machine, etc. The processor 118 can perform signal encoding, data processing, power control, input / output processing, and / or any other functions that enable the WTRU 102 to operate in a wireless environment. The processor 118 can be coupled to the transceiver 120, and the transceiver 120 can be coupled to the transmit / receive element 122. Although Figure 1B the processor 118 and the transceiver 120 are depicted as separate components, it should be understood that the processor 118 and the transceiver 120 can be integrated together in an electronic package or chip.

[0091] The transmit / receive element 122 can be configured to transmit signals to or receive signals from a base station (e.g., base station 114a) via the air interface 116. For example, in one embodiment, the transmit / receive element 122 can be an antenna configured to transmit and / or receive RF signals. In one embodiment, the transmit / receive element 122 can be a transmitter / detector configured to transmit and / or receive IR, UV, or visible light signals, for example. In yet another embodiment, the transmit / receive element 122 can be configured to transmit and / or receive RF and optical signals. It should be understood that the transmit / receive element 122 can be configured to transmit and / or receive any combination of wireless signals.

[0092] Although the transmit / receive element 122 is depicted as a single element in Figure 1B the WTRU 102 can include any number of transmit / receive elements 122. More specifically, the WTRU 102 can employ MIMO technology. Thus, in one embodiment, the WTRU 102 can include two or more transmit / receive elements 122 (e.g., multiple antennas) for transmitting and receiving wireless signals via the air interface 116.

[0093] The transceiver 120 can be configured to modulate the signals to be transmitted by the transmit / receive element 122 and demodulate the signals received by the transmit / receive element 122. As described above, the WTRU 102 can have multi-mode capabilities. Thus, the transceiver 120 can include multiple transceivers for enabling the WTRU 102 to communicate via multiple RATs, such as, for example, NR and IEEE 802.11.

[0094] The processor 118 of the WTRU 102 may be coupled to a speaker / microphone 124, a keyboard 126, and / or a display / touchpad 128 (e.g., a liquid crystal display (LCD) display unit or an organic light emitting diode (OLED) display unit), and may receive user input data therefrom. The processor 118 may also output user data to the speaker / microphone 124, the keyboard 126, and / or the display / touchpad 128. In addition, the processor 118 may access information from and store data in any type of suitable memory (e.g., non-removable memory 130 and / or removable memory 132). The non-removable memory 130 may include random access memory (RAM), read-only memory (ROM), a hard disk, or any other type of memory storage device. The removable memory 132 may include a subscriber identity module (SIM) card, a memory stick, a secure digital (SD) memory card, etc. In other embodiments, the processor 118 may access information from and store data in a memory that is not physically located on the WTRU 102 (e.g., on a server or a home computer (not shown)).

[0095] The processor 118 may receive power from a power supply 134 and may be configured to distribute and / or control power to other components in the WTRU 102. The power supply 134 may be any suitable device for powering the WTRU 102. For example, the power supply 134 may include one or more dry cells (e.g., nickel cadmium (NiCd), nickel zinc (NiZn), nickel metal hydride (NiMH), lithium ion (Li-ion), etc.), a solar cell, a fuel cell, etc.

[0096] The processor 118 may also be coupled to a GPS chipset 136, which may be configured to provide location information (e.g., longitude and latitude) regarding the current location of the WTRU 102. In addition to, or instead of, the information from the GPS chipset 136, the WTRU 102 may receive location information from a base station (e.g., base stations 114a, 114b) via an air interface 116, and / or may determine its location based on the timing of signals received from two or more nearby base stations. It should be understood that the WTRU 102 may obtain location information by any suitable location determination method while remaining consistent with the embodiments.

[0097] The processor 118 may be further coupled to other peripheral devices 138, which may include one or more software and / or hardware modules that provide additional features, functionality, and / or wired or wireless connections. For example, the peripheral devices 138 may include an accelerometer, an electronic compass, a satellite transceiver, a digital camera (for photos and / or videos), a universal serial bus (USB) port, a vibration device, a television transceiver, a hands-free headset, a Bluetooth module, a frequency modulation (FM) radio unit, a digital music player, a media player, an electronic game player module, an Internet browser, a virtual reality and / or augmented reality (VR / AR) device, an activity tracker, etc. The peripheral devices 138 may include one or more sensors. The sensors may be one or more of a gyroscope, an accelerometer, a Hall effect sensor, a magnetometer, an orientation sensor, a proximity sensor, a temperature sensor, a time sensor; a geographic location sensor, an altimeter, a light sensor, a touch sensor, a magnetometer, a barometer, an attitude sensor, a biosensor, a humidity sensor, etc.

[0098] The WTRU 102 may include a full-duplex radio for which the transmission and reception of some or all signals (e.g., signals associated with a particular subframe for UL (e.g., for transmission) and DL (e.g., for reception)) may be concurrent and / or simultaneous. The full-duplex radio may include an interference management unit to reduce and / or substantially eliminate self-interference via hardware (e.g., a choke) or by signal processing of a processor (e.g., a separate processor (not shown) or via the processor 118). In one embodiment, the WTRU 102 may include a half-duplex radio for which the transmission and reception of some or all signals (e.g., signals associated with a particular subframe for UL (e.g., for transmission) or DL (e.g., for reception)).

[0099] Figure 1C is a system diagram showing the RAN 104 and the CN 106 according to an embodiment. As described above, the RAN 104 may communicate with the WTRU 102a, 102b, 102c via the air interface 116 using E-UTRA radio technology. The RAN 104 may also communicate with the CN 106.

[0100] The RAN 104 may include eNode-Bs 160a, 160b, 160c, but it should be understood that the RAN 104 may include any number of eNode-Bs while remaining consistent with the embodiments. Each of the eNode-Bs 160a, 160b, 160c may include one or more transceivers for communicating with the WTRUs 102a, 102b, 102c via the air interface 116. In one embodiment, the eNode-Bs 160a, 160b, 160c may implement MIMO technology. Thus, for example, the eNode-B 160a may use multiple antennas to transmit wireless signals to and / or receive wireless signals from the WTRU 102a.

[0101] Each of the eNode-Bs 160a, 160b, 160c may be associated with a particular cell (not shown) and may be configured to handle radio resource management decisions, handover decisions, user scheduling, etc. in the UL and / or DL. As Figure 1C shown, the eNode-Bs 160a, 160b, 160c may communicate with each other via the X2 interface.

[0102] Figure 1C shown, the CN 106 may include a Mobility Management Entity (MME) 162, a Serving Gateway (SGW) 164, and a Packet Data Network (PDN) Gateway (PGW) 166. Although the foregoing elements are described as part of the CN 106, it should be understood that any of these elements may be owned and / or operated by an entity other than the CN operator.

[0103] The MME 162 may be connected to each of the eNode-Bs 162a, 162b, 162c in the RAN 104 via the S1 interface and may act as a control node. For example, the MME 162 may be responsible for authenticating the users of the WTRUs 102a, 102b, 102c, bearer activation / deactivation, selecting a particular serving gateway, etc. during the initial attachment of the WTRUs 102a, 102b, 102c. The MME 162 may provide control plane functions for handover between the RAN 104 and other RANs (not shown) employing other radio technologies such as GSM and / or WCDMA.

[0104] The SGW 164 can be connected to each of the eNode Bs 160a, 160b, 160c in the RAN 104 via the S1 interface. The SGW 164 can generally route and forward user data packets to / from the WTRUs 102a, 102b, 102c. The SGW 164 can perform other functions such as anchoring the user plane during handovers between eNode Bs, triggering paging when DL data is available for the WTRUs 102a, 102b, 102c, managing and storing the contexts of the WTRUs 102a, 102b, 102c, etc.

[0105] The SGW 164 can be connected to the PGW 166, which can provide the WTRUs 102a, 102b, 102c with access to a packet switched network such as the Internet 110 to facilitate communication between the WTRUs 102a, 102b, 102c and IP enabled devices.

[0106] The CN 106 can facilitate communication with other networks. For example, the CN 106 can provide the WTRUs 102a, 102b, 102c with access to a circuit switched network such as the PSTN 108 to facilitate communication between the WTRUs 102a, 102b, 102c and traditional landline communication devices. For example, the CN 106 can include, or communicate with, an IP gateway (e.g., an IP Multimedia Subsystem (IMS) server) that acts as an interface between the CN 106 and the PSTN 108. In addition, the CN 106 can provide the WTRUs 102a, 102b, 102c with access to other networks 112, which can include other wired and / or wireless networks owned and / or operated by other service providers.

[0107] Although the WTRU is Figures 1A - 1D described as a wireless terminal, it is contemplated that in some representative embodiments, such a terminal can use (e.g., temporarily or permanently) a wired communication interface to the communication network.

[0108] In a representative embodiment, the other network 112 can be a WLAN.

[0109] Infrastructure Basic Service Set (BSS) mode WLANs can have an Access Point (AP) for the BSS and one or more Stations (STAs) associated with the AP. The AP can access or interface to a Distribution System (DS) or another type of wired / wireless network that conveys traffic to and / or from the BSS. Traffic destined for an STA from outside the BSS can reach the STA via the AP and can be delivered to the STA. Traffic from an STA to a destination outside the BSS can be sent to the AP to be delivered to the corresponding destination. For example, traffic between STAs within a BSS can be conveyed through the AP, where the source STA can send traffic to the AP and the AP can deliver the traffic to the destination STA. Traffic between STAs within a BSS can be considered and / or referred to as peer-to-peer traffic. Peer-to-peer traffic can be sent between a source and destination STA (e.g., directly between them) using Direct Link Setup (DLS). In some representative embodiments, DLS can use 802.11e DLS or 802.11z Tunnel DLS (TDLS). WLANs using Independent BSS (IBSS) mode may not have an AP, and STAs within the IBSS or using the IBSS (e.g., all STAs) can communicate directly with each other. The IBSS communication mode is sometimes referred to here as the "ad hoc" communication mode.

[0110] When using 802.11ac infrastructure operation mode or a similar operation mode, the AP can transmit beacons on a fixed channel (e.g., the primary channel). The primary channel can be of a fixed width (e.g., 20 MHz bandwidth) or have a dynamically set width. The primary channel can be the operating channel of the BSS and can be used by STAs to establish a connection with the AP. In some representative embodiments, for example, in 802.11 systems, Carrier Sense Multiple Access with Collision Avoidance (CSMA / CA) can be implemented. For CSMA / CA, STAs including the AP (e.g., each STA) can sense the primary channel. If a particular STA senses / detects and / or determines that the primary channel is busy, that particular STA can back off. One STA (e.g., only one station) can transmit at any given time within a given BSS.

[0111] High Throughput (HT) STAs can communicate using 40 MHz wide channels, e.g., by combining the primary 20 MHz channel with an adjacent or non-adjacent 20 MHz channel to form a 40 MHz wide channel.

[0112] A very high throughput (VHT) STA may support channels that are 20 MHz, 40 MHz, 80 MHz, and / or 160 MHz wide. 40 MHz and / or 80 MHz channels may be formed by combining contiguous 20 MHz channels. A 160 MHz channel may be formed by combining eight contiguous 20 MHz channels, or by combining two non - contiguous 80 MHz channels, which may be referred to as an 80+80 configuration. For the 80+80 configuration, after channel coding, data may pass through a segment parser, which may divide the data into two streams. Inverse fast Fourier transform (IFFT) processing and time - domain processing may be performed separately on each stream. These streams may be mapped to two 80 MHz channels, and the data may be transmitted by the transmitting STA. At the receiver of the receiving STA, the operations of the above 80+80 configuration may be reversed, and the combined data may be transmitted to the media access control (MAC).

[0113] 802.11af and 802.11ah support operating modes below 1 GHz. The channel operating bandwidth and carriers in 802.11af and 802.11ah are reduced compared to 802.11n and 802.11ac. 802.11af supports 5 MHz, 10 MHz, and 20 MHz bandwidths in the television white space (TVWS), and 802.11ah uses non - TVWS spectrum to support 1 MHz, 2 MHz, 4 MHz, 8 MHz, and 16 MHz bandwidths. According to a representative embodiment, 802.11ah may support meter - type control / machine - type communication (MTC), such as MTC devices in a macro - coverage area. MTC devices may have certain capabilities, for example, limited capabilities, including supporting (e.g., only supporting) certain and / or limited bandwidths. MTC devices may include a battery with a battery life higher than a threshold (e.g., to maintain a very long battery life).

[0114] A WLAN system that can support multiple channels and channel bandwidths (e.g., 802.11n, 802.11ac, 802.11af, and 802.11ah) includes a channel that can be designated as the primary channel. The bandwidth of the primary channel can be equal to the maximum common operating bandwidth supported by all STAs in the BSS. The bandwidth of the primary channel can be set and / or restricted by one STA among all STAs operating in the BSS that supports the minimum bandwidth operating mode. In the example of 802.11ah, for an STA that supports (e.g., only supports) the 1MHz mode (e.g., an MTC type device), the primary channel can be 1MHz wide, even if the AP and other STAs in the BSS support 2MHz, 4MHz, 8MHz, 16MHz, and / or other channel bandwidth operating modes. Carrier sensing and / or Network Allocation Vector (NAV) setting may depend on the state of the primary channel. If the primary channel is busy, e.g., due to an STA (only supporting the 1MHz operating mode) transmitting to the AP, all available frequency bands can be considered busy, even if most of the available frequency bands remain idle.

[0115] In the United States, the available frequency band that 802.11ah can use is from 902MHz to 928MHz. In Korea, the available frequency band is from 917.5MHz to 923.5MHz. In Japan, the available frequency band is from 916.5MHz to 927.5MHz. The total available bandwidth for 802.11ah is from 6MHz to 26MHz, depending on the country code.

[0116] Figure 1D FIG. is a system diagram showing RAN 104 and CN 106 according to one embodiment. As described above, RAN 104 can communicate with WTRUs 102a, 102b, 102c via air interface 116 using NR radio technology. RAN 104 can also communicate with CN 106.

[0117] The RAN 104 may include gNBs 180a, 180b, 180c, but it should be understood that the RAN 104 may include any number of gNBs while remaining consistent with the embodiments. The gNBs 180a, 180b, 180c may each include one or more transceivers for communicating with the WTRUs 102a, 102b, 102c via the air interface 116. In one embodiment, the gNBs 180a, 180b, 180c may implement MIMO technology. For example, the gNBs 180a, 108b may utilize beamforming to transmit signals to and / or receive signals from the gNBs 180a, 180b, 180c. Thus, for example, the gNB 180a may use multiple antennas to transmit wireless signals to and / or receive wireless signals from the WTRU 102a. In one embodiment, the gNBs 180a, 180b, 180c may implement carrier aggregation technology. For example, the gNB 180a may transmit multiple component carriers (not shown) to the WTRU 102a. A subset of these component carriers may be on unlicensed spectrum while the remaining component carriers may be on licensed spectrum. In one embodiment, the gNBs 180a, 180b, 180c may implement coordinated multi-point (CoMP) technology. For example, the WTRU 102a may receive coordinated transmissions from the gNB 180a and the gNB 180b (and / or gNB 180c).

[0118] The WTRUs 102a, 102b, 102c may communicate with the gNBs 180a, 180b, 180c using transmissions associated with scalable numerology. For example, the OFDM symbol interval and / or the OFDM subcarrier interval may be different for different transmissions, different cells, and / or different portions of the radio transmission spectrum. The WTRUs 102a, 102b, 102c may communicate with the gNBs 180a, 180b, 180c using subframes or transmission time intervals (TTIs) of various or scalable lengths (e.g., containing a variable number of OFDM symbols and / or having a continuously variable absolute time).

[0119] gNBs 180a, 180b, 180c can be configured to communicate with WTRUs 102a, 102b, 102c in stand-alone configuration and / or non-stand-alone configuration. In stand-alone configuration, WTRUs 102a, 102b, 102c can communicate with gNBs 180a, 180b, 180c without accessing other RANs (e.g., such as eNode-Bs 160a, 160b, 160c). In stand-alone configuration, WTRUs 102a, 102b, 102c can use one or more gNBs 180a, 180b, 180c as mobility anchors. In stand-alone configuration, WTRUs 102a, 102b, 102c can communicate with gNBs 180a, 180b, 180c using signals in unlicensed bands. In non-stand-alone configuration, WTRUs 102a, 102b, 102c can communicate / connect with gNBs 180a, 180b, 180c while also communicating / connecting with another RAN such as eNode-Bs 160a, 160b, 160c. For example, WTRUs 102a, 102b, 102c can implement the DC principle to communicate with one or more gNBs 180a, 180b, 180c and one or more eNode-Bs 160a, 160b, 160c substantially simultaneously. In non-stand-alone configuration, eNode-Bs 160a, 160b, 160c can act as the mobility anchor for WTRUs 102a, 102b, 102c, and gNBs 180a, 180b, 180c can provide additional coverage and / or throughput for serving WTRUs 102a, 102b, 102c.

[0120] Each of gNBs 180a, 180b, 180c can be associated with a specific cell (not shown) and can be configured to handle radio resource management decisions, handover decisions, user scheduling in UL and / or DL, network slice support, interworking between DC, NR and E-UTRA, routing user plane data to user plane functions (UPFs) 184a, 184b, routing control plane information to access and mobility management functions (AMFs) 182a, 182b, etc. As Figure 1D shown, gNBs 180a, 180b, 180c can communicate with each other via the Xn interface.

[0121] Figure 1DThe CN 106 shown may include at least one AMF 182a, 182b, at least one UPF 184a, 184b, at least one session management function (SMF) 183a, 183b, and possibly data networks (DN) 185a, 185b. Although the foregoing elements are described as part of the CN 106, it should be understood that any of these elements may be owned and / or operated by an entity other than the CN operator.

[0122] The AMF 182a, 182b may be connected to one or more gNBs 180a, 180b, 180c in the RAN 104 via an N2 interface and may act as a control node. For example, the AMF 182a, 182b may be responsible for authenticating users of the WTRU 102a, 102b, 102c, supporting network slicing (e.g., handling different protocol data unit (PDU) sessions with different requirements), selecting a particular SMF 183a, 183b, managing the registration area, terminating non-access stratum (NAS) signaling, mobility management, and so on. The AMF 182a, 182b may use network slicing in order to customize the CN support for the WTRU 102a, 102b, 102c based on the type of service used by the WTRU 102a, 102b, 102c. For example, different network slices may be established for different use cases, such as services relying on ultra-reliable low-latency (URLLC) access, services relying on enhanced massive mobile broadband (eMBB) access, services for machine type communication (MTC) access, etc. The AMF 182a, 182b may provide control plane functions for handover between the RAN 104 and other RANs (not shown) employing other radio technologies (e.g., LTE, LTE-A, LTE-A Pro, and / or non-3GPP access technologies such as WiFi).

[0123] The SMF 183a, 183b may be connected to the AMF 182a, 182b in the CN 106 via an N11 interface. The SMF 183a, 183b may also be connected to the UPF 184a, 184b in the CN 106 via an N4 interface. The SMF 183a, 183b may select and control the UPF 184a, 184b and configure the traffic routing through the UPF 184a, 184b. The SMF 183a, 183b may perform other functions, such as managing and allocating UE IP addresses, managing PDU sessions, controlling policy enforcement and QoS, providing DL data notifications, etc. The PDU session type may be IP-based, non-IP-based, Ethernet-based, and so on.

[0124] UPF 184a and 184b can be connected to one or more gNBs 180a, 180b, 180c in the RAN 104 via the N3 interface, which can provide access to a packet switched network (such as the Internet 110) to the WTRUs 102a, 102b, 102c to facilitate communication between the WTRUs 102a, 102b, 102c and IP-enabled devices. UPF 184, 184b can perform other functions such as routing and forwarding packets, implementing user plane policies, supporting multi-homed PDU sessions, handling user plane QoS, buffering DL packets, providing mobility anchoring, etc.

[0125] The CN 106 can facilitate communication with other networks. For example, the CN 106 can include an IP gateway (such as an IP Multimedia Subsystem (IMS) server) that acts as an interface between the CN 106 and the PSTN 108, or can communicate therewith. In addition, the CN 106 can provide access to other networks 112 to the WTRUs 102a, 102b, 102c, and the other networks 112 can include other wired and / or wireless networks owned and / or operated by other service providers. In one embodiment, the WTRUs 102a, 102b, 102c can be connected to the local DNs 185a, 185b via the N3 interface to the UPFs 184a, 184b and the N6 interface between the UPFs 184a, 184b and the DNs 185a, 185b through the UPFs 184a, 184b.

[0126] In view of Figures 1A - 1D and Figures 1A - 1D In view of the corresponding descriptions of, one or more or all of the functions described herein regarding one or more of the following can be performed by one or more simulation devices (not shown): WTRUs 102a-d, base stations 114a-b, eNode-Bs 160a-c, MME 162, SGW 164, PGW 166, gNBs 180a-c, AMFs 182a-b, UPFs 184a-b, SMFs 183a-b, DNs 185a-b, and / or any other device(s) described herein. The simulation device(s) can be one or more devices configured to simulate one or more or all of the functions described herein. For example, the simulation device(s) can be used to test other devices and / or simulate network and / or WTRU functions.

[0127] A simulation device can be designed to implement one or more tests of other devices in a laboratory environment and / or an operator network environment. For example, one or more simulation devices can perform one or more or all functions while being fully or partially implemented and / or deployed as part of a wired and / or wireless communication network in order to test other devices within the communication network. One or more simulation devices can perform one or more or all functions while being temporarily implemented / deployed as part of a wired and / or wireless communication network. For the purpose of testing and / or performing tests using over-the-air wireless communication, the simulation device can be directly coupled to another device.

[0128] One or more simulation devices can perform one or more functions, including all functions, rather than being implemented / deployed as part of a wired and / or wireless communication network. For example, the simulation device can be used to test test scenarios in a laboratory and / or a non-deployed (e.g., test) wired and / or wireless communication network in order to implement testing of one or more components. One or more simulation devices can be test devices. The simulation device can transmit and / or receive data using, for example, direct RF coupling via an RF circuit and / or wireless communication, and the RF circuit can include one or more antennas.

[0129] Figure 2 is a system diagram of an exemplary WTRU showing interaction with a terminal device (TE) and a mobile terminal (MT) via an attention (AT) command. As Figure 2 shown in the example, a WTRU such as WTRU 102a can include two functional components. The first functional component can be the TE 220, which is part of the WTRU 102a and can host some WTRU 102a applications and processes. The TE 220 controls the MT 240 functions and network services in part through an intermediate node called a terminal adapter (TA). Although not explicitly shown in Figure 2 the TA can be located between the TE 220 and the MT 240. The TE 220 can communicate with and control the MT240 via an AT command.

[0130] An end-to-end redundant user plane path can be based on dual connectivity. To support wireless services such as URLLC, a WTRU may establish two redundant PDU sessions over a fifth generation (5G) network such that the 5G system (5GS) establishes the user plane paths of the two redundant PDU sessions as separate. In one example, the WTRU may be the WTRU 102a. In the case where the two redundant PDU sessions have separate user plane paths, the subscription of the user indicates whether the user is allowed to have redundant PDU sessions, and this indication is provided to the SMF from the Unified Data Management (UDM). The Next Generation RAN (NG-RAN) may utilize two NG-RAN nodes (e.g., a primary NG-RAN and a secondary NG-RAN, or a single NG-RAN node) to implement redundant user plane resources for the two PDU sessions. In both cases, there is a single N1 interface to the AMF.

[0131] The 5GS also supports redundant transmission on the N3 / N9 interface, where two redundant N3 / N9 tunnels with independent user plane paths are established between the UPF and the NG-RAN to transmit replicated user packets. This redundant transmission using two N3 / N9 tunnels is performed at the QoS flow granularity that shares the same QoS flow identifier (ID). In this case, these packets can be transmitted via the two N3 tunnels between a single UPF and the NG-RAN respectively. It is assumed that the NG-RAN node and the PDU session anchor (PSA) UPF will support the packet duplication and elimination function.

[0132] Additionally or alternatively, the 5GS may support redundant transmission at the transport layer. In this case, redundancy between the RAN and the UPF may be supported at the transport layer or the UDP layer. In other words, it can be done without being affected by 3GPP specifications. In this case, for a PDU session established between a WTRU and the network for URLLC services, the SMF selects a UPF that supports redundant transmission at the transport layer based on the data network name (DNN), single network slice selection assistance information (S-NSSAI), knowledge of supporting redundant transmission at the transport layer, etc. Here, an N3 General Packet Radio Service (GPRS) Tunnel Protocol for the user plane (GTP-U) tunnel is established between the UPF and the NG-RAN. For DL data transmission, the redundancy function in the UPF replicates the DL data at the transport layer. On the other hand, for UL data transmission, the redundancy function in the NG-RAN performs redundancy processing at the backhaul transport layer for the UL. In this case, it is assumed that the NG-RAN node and the UPF will support the packet duplication and elimination function.

[0133] Redundant user plane paths can be based on multiple WTRUs per device. One way to implement multi-user plane paths in a system is based on a device with multiple WTRUs and a specific network deployment. This method assumes a RAN deployment where, in the case of NR, redundant coverage of multiple gNBs or redundant coverage of multiple base stations is typically available. Upper layer protocols such as IEEE 802.1 Time-Sensitive Networking (TSN) can utilize multiple user plane paths.

[0134] In this case, the WTRUs belonging to the same terminal device request to establish PDU sessions using independent RAN and CN network resources. The following assumptions are used to implement this scenario. The RAN coverage is redundant in the target area: it is possible to connect to multiple gNBs or multiple base stations from the same location. Selecting different gNBs or base stations for the WTRUs in the same device is achieved through the concept of a WTRU reliability group for the WTRU and also for the cells of the gNB or base station.

[0135] An example implementation can be as follows: The NSSAI allowed for the WTRU can be used as an input to select the RAT / frequency selection priority (RFSP) index value for the WTRU. The RAN node uses the RFSP for radio resource management (RRM) purposes and can determine the WTRU reliability group based on local configuration, based on the S-NSSAI in the allowed NSSAI and / or the S-NSSAI for the PDU session(s).

[0136] Frame Replication and Elimination for Reliability (FRER) is a standard envisioned for providing high reliability, initially envisioned in a Time-Sensitive Networking (TSN) environment. The FRER mechanism provides identification and replication of frames for redundant transmission over multiple paths. When duplicate frames are received, the duplicate frames can be identified based on the sequence number and eliminated.

[0137] This mechanism can be configured in a flexible manner. More than two paths can be applied to achieve additional redundancy. The FRER entity can simultaneously play the replication role and the elimination role in two different directions.

[0138] In a typical deployment, the FRER function is established using a management protocol and controlled by a centralized entity. Note that the FRER function can be set up on an intermediate switch or a terminal host even if the central controller and the management protocol can be different. Multiple replication and elimination points can be defined for a single flow according to the requirements and network characteristics.

[0139] A new feasibility study has been initiated in 3GPP SA1 working group, named Localized Mobile Metaverse Services, e.g., in 3GPP TR 22.856. One use case of interest in this study is the use of the metaverse for critical healthcare services. In this use case, it is asserted that some critical healthcare scenarios will utilize immersive interactive mobile services. Such scenarios include immersive remote surgery, metaverse doctor consultations, metaverse body scans, and vital signs, etc. The scenario of immersive remote surgery describes a doctor who is far from the patient's location and in need of an emergency operation, and how the doctor can virtually perform the operation on the patient. A potential new requirement related to this use case is described as "The 5G system shall provide fault-tolerant and reliable end-to-end support for critical healthcare services."

[0140] In the embodiments and examples provided herein, new functions are described to improve reliability and fault tolerance without significantly increasing the amount of radio resources consumed by the communication device. As described above, to improve the reliability of application layer data transmission and reception, the 5G system supports an end-to-end redundant user plane path based on dual connectivity. The disadvantage of using this feature to improve reliability is that this method contains multiple single points of failure. For example, this method relies on a single AMF node, and all data is routed to a single data network.

[0141] In addition, as described above, the communication device may include a WTRU. Each WTRU, e.g., WTRU 102a, can be used to transmit and receive the same application data. Application layer protocols can be used to discard redundant data. Assuming each WTRU is connected to a different network, this method will be more reliable than the end-to-end redundant user plane path method based on dual connectivity because it includes fewer single points of failure. The reduction in the number of failure points is due to each WTRU leveraging different network nodes (e.g., AMF). In addition, depending on the configuration of each WTRU, the data transmitted and received by each WTRU may pass through different N6 data networks. However, the disadvantage of this method is that the amount of radio resources required to transmit and receive data may be twice that of a communication device that includes only one WTRU.

[0142] Therefore, there is a need for a method to improve the reliability and fault tolerance of application layer sessions without significantly increasing the amount of radio resources required by the communication device hosting the application. In other words, it is desirable that communication devices requiring high reliability do not use more radio resources than communication devices hosting the same type of application layer session but not taking steps to improve reliability.

[0143] In the embodiments and examples provided herein, increasing the fault tolerance of an application layer session can mean reducing the number of single points of failure associated with the communication device hosting the application layer session.

[0144] The embodiments and examples provided herein introduce new concepts for alternative PDU sessions for dual WTRUs in a device and introduce PDU session states of discard or no discard. For example, the embodiments and examples provided herein describe the process of creating and preparing an alternative PDU session and setting its state to discard or no discard. In addition, the embodiments and examples provided herein describe the process that can be used by the network and triggered by the WTRU to change the PDU session state. In addition, the embodiments and examples provided herein describe the process of changing a PDU session to an alternative PDU session and describe the change of the PDU session state with the help of an application server (AS), such as from a discard state to a no discard state. In addition, the embodiments and examples provided herein describe a process that can be used by the network hosting each PDU session for dual WTRUs in a device to coordinate the change of the PDU session state. In addition, the embodiments and examples provided herein describe the process that can be used by two MTs in the WTRU to coordinate the change of the PDU session state.

[0145] Example solutions include alternative PDU session features. In addition, the examples provided herein include WTRU support. In one example, the WTRU may establish a PDU session with the network. The WTRU may receive an indication from the network that the PDU session is an alternative PDU session and may determine whether the PDU session is in a discard state, where when the PDU session is in a discard state, the WTRU does not transmit data associated with the PDU session. In addition, the WTRU may detect that the PDU session is no longer in a discard state and may determine to transmit data associated with the PDU session.

[0146] When the WTRU establishes a PDU session with the network or when the WTRU requests to modify a PDU session, the WTRU may indicate to the network in a PDU session establishment request message or a PDU session modification request message that the PDU session is an alternative PDU session.

[0147] By applying an AT command that requests to use an alternative PDU session, the WTRU can be triggered to establish or modify a PDU session and make the PDU session an alternative PDU session.

[0148] By detecting that the application service matches the service descriptor in the UE Routing Selection Policy (URSP) rule or the WTRU Routing Selection Policy rule, the WTRU can be triggered to establish or modify a PDU session and make the PDU session an alternative PDU session. The WTRU can receive an indication that the PDU session is an alternative PDU session in the PDU session establishment acceptance message or the PDU session modification command message. The WTRU can determine that the PDU session is in a discarded state based on the indication in the PDU session establishment acceptance message or the PDU session modification command message. The WTRU can determine that the PDU session is no longer in a discarded state based on an indication from the application provided to the MT part of the WTRU in an AT command. Additionally, the WTRU can determine that the PDU session is no longer in a discarded state based on receiving downlink data associated with the PDU session.

[0149] Examples provided herein include SMF support. In one example, the SMF can receive a request to make a PDU session an alternative PDU session. The SMF can send an indication that the PDU session is an alternative PDU session and an indication of whether the PDU session is in a discarded state to a network node. Additionally, the SMF can send an indication that the PDU session is an alternative PDU session to the WTRU. Additionally, the SMF can receive an indication that the PDU session is no longer in a discarded state. Additionally, the SMF can send a notification that the PDU session is no longer in a discarded state to a network node.

[0150] In one example, the network node can be a RAN node, and the indication can be sent by the SMF to the RAN node in an N2 message. Additionally, the network node can be a UPF node, and the indication can be sent by the SMF to the UPF node in an N4 message.

[0151] Additionally, a request to make a PDU session an alternative PDU session can be received in the PDU session establishment request message or the PDU session modification request message. An indication that the PDU session is an alternative PDU session can be sent to the WTRU in the PDU session establishment acceptance message or the PDU session modification command message. An indication that the PDU session is no longer in a discarded state can be received in the PDU session modification command. An indication to notify the UPF that the PDU session is no longer in a discarded state can be sent in an N4 message. A request to make a PDU session an alternative PDU session can be received from the Policy Control Function (PCF). A request to make a PDU session an alternative PDU session can be received from the Network Exposure Function (NEF).

[0152] Examples provided herein include data plane network nodes that support alternative PDU session features. In an example, the data plane network node can be a UPF or a RAN node. In one example, the data plane network node can receive an indication that a PDU session is an alternative PDU session and an indication of whether the PDU session is in a discarded state from an SMF. Additionally, the data plane network node can detect that the PDU session is no longer in the discarded state. Additionally, the data plane network node can send a notification to the SMF that the PDU session is no longer in the discarded state.

[0153] The network node can be a RAN node, and the indication can be received by the RAN node from the SMF in an N2 message. The network node can be a UPF, and the indication can be received by the UPF node from the SMF in an N4 message.

[0154] In one example, a UPF or a RAN node can detect that the PDU session is no longer in the discarded state based on receiving uplink or downlink data associated with the PDU session. Additionally, a UPF or a RAN node can detect that the PDU session is no longer in the discarded state based on applying a packet detection rule to downlink or uplink data.

[0155] The embodiments and examples provided herein discuss how to improve the fault tolerance and reliability of communication devices. In most examples herein, the communication device is a device that physically hosts two or more WTRUs or two or more MTs. It should be understood that the same improvements can be applied to a deployment that deploys two separate communication devices to achieve fault tolerance and reliability. For example, a first communication device can host a WTRU and perform functions such as displaying content, while a second communication device can host a second WTRU, act as a backup for the first communication device, and be capable of displaying the same content as the first communication device.

[0156] The example solutions provided herein introduce the concept of an alternative PDU session. The alternative PDU session serves as an alternative to a first PDU session. The first PDU session and the alternative PDU session can terminate at the same or different WTRUs. The alternative PDU session is a PDU session that can be used to send and receive data to and from the same data network as the data sent and received via the first PDU session.

[0157] The alternative PDU session can be maintained in a discarded or non-discarded state. In the discarded state, data from the PDU session is discarded or discarded by the WTRU, RAN node, or UPF, such that the data is not sent over the air and does not consume any radio resources. In the non-discarded state, data from the PDU session is not discarded or discarded, but is allowed to be transmitted via the PDU session.

[0158] When it is detected that the first PDU session has experienced some problems, the WTRU or the network triggers the alternative PDU session to transition from the discarded state to the non-discarded state. One or more exemplary problems can include: a large number of discarded packets or a failure of a network node associated with the network serving the first PDU session. Optionally or additionally, when a failure occurs in the core network, the WTRU or the AS can subscribe to be notified. In such a case, the 5GC can notify the WTRU and / or the AS that a failure has occurred and can trigger the alternative PDU state session to transition from the discarded state to the non-discarded state. Similarly, the 5GC can notify the WTRU and / or the AS that the failure condition in the core network has been resolved. This allows the WTRU and / or the AS to trigger the transition of the alternative PDU session from the non-discarded state to the discarded state. As another alternative or addition, the WTRU and the AS can determine to transition from the discarded state to the non-discarded state based on the knowledge of the traffic carried in the flow. For example, a flow may have bursty traffic that is more important than other traffic. In such a case, the WTRU and the AS can decide to proactively transition the traffic from the discarded state to the non-discarded state to protect the important traffic.

[0159] When it is detected that the first PDU session no longer experiences problems, the alternative PDU session can be triggered by the WTRU or the network to transition from the non-discarded state to the discarded state. One or more example problems that the PDU no longer experiences can include the number of discarded packets being below a threshold or the failure condition associated with the network serving the first PDU session having been resolved.

[0160] The first PDU session can also transition between the discarded and non-discarded states. However, the first PDU session can be established with a preferred network and is always used unless and until the first PDU session or the network serving the first PDU session detects some problems.

[0161] Figure 3 is a diagram showing an example of the establishment and state change of an alternative PDU session. The example shown in Chart 300 illustrates the process of switching between the discarded and non-discarded states. For example, in the first step, a first PDU session is established using a first terminal with a RAN node and the 5GC (5GC1). In one example, the first terminal can be a WTRU, such as WTRU1310, and the RAN node can be a base station, such as BS1320. In another example, the first terminal can be a UE, such as UE1, and the RAN node can be a gNB, such as gNB1. Additionally, WTRU1 can be the WTRU shown in the example of FIG. 1, such as WTRU 102a. This PDU session is then placed in the non-discarded state, which means that all entities serving this PDU session, such as WTRU1310, BS1320, and UPF1330, do not intentionally discard data. In Figure 3In the example shown, the UPF 1330 can be in the 5GC, such as 5GC 1. Additionally, in the case of congestion at a certain node, packet dropping still occurs, which is different from dropping data according to the dropping status introduced herein.

[0162] In a second step that can occur in parallel with the first step, a second terminal WTRU 2360 establishes a PDU session that is an alternative to the first PDU session established by the WTRU 1310. The WTRU 2360 can establish this alternative PDU session with the BS 2370 and the UPF 2380. This alternative PDU session is placed in a dropped state. Since this alternative PDU session or the second PDU session is in a dropped state, the WTRU 2360 will not transmit data associated with this alternative PDU session, and the UPF 2380 or the BS 2370 will drop data associated with this alternative PDU session. In one example, the BS 2370 can be a gNB. In another example, the BS 2370 can be another type of base station.

[0163] In the third and fourth steps, the first PDU session is used to exchange data because it is in a non-dropped state. For example, in the third step, a data transmission 312 is exchanged between the WTRU 1310 and the BS 1320. Additionally, a data transmission 323 is exchanged between the BS 1320 and the UPF 1330. In one example of the third step, the WTRU 1310 can transmit the data transmission 312 to the BS 1320. Additionally, the BS 1320 can transmit the data transmission 323 to the UPF 1330. In one example, the data 323 can include all or some of the data 312.

[0164] In an additional or alternative example of the third step, the UPF 1330 can transmit the data transmission 323 to the BS 1320. Additionally, the BS 1320 can transmit the data transmission 312 to the WTRU 1310. Thus, the data 312 can include some or all of the data 323.

[0165] In the fourth step, as described above, data associated with the alternative PDU session is dropped. As long as the WTRU 2360 has an alternative PDU session (in a dropped state or a non-dropped state), and as long as the WTRU 2360 has not deregistered due to inactivity (e.g., in a non-dropped state), the WTRU 2360 can remain registered to the 5GC 2. In one example of the fourth step, the WTRU 2360 can drop the data 347 for transmission to the BS 2370. In another example of the fourth step, the UPF 2380 can drop the data 387 for transmission to the BS 2370. Similarly, the BS 2370 can drop the data 377 for transmission to the UPF 2380. Additionally or alternatively, the BS 2370 can drop the data 377 for transmission to the WTRU 2360.

[0166] In the embodiments and examples provided herein, discarding data may include that the RAN node may decide to stop transmitting data scheduled to be transmitted when it receives and determines that the status has switched to the discard state. For example, when the WTRU 2360 discards data 347 to be transmitted to the BS 2370, the WTRU 2360 may stop transmitting the data scheduled to be transmitted. In another example, when the UPF 2380 discards data 387 to be transmitted to the BS 2370, the UPF 2380 may stop transmitting the data scheduled to be transmitted. Similarly, when the BS 2370 discards data 377 to be transmitted, the BS 2370 may stop transmitting the data scheduled to be transmitted.

[0167] Additionally or alternatively, in the embodiments and examples provided herein, discarding data may include that the RAN node may also completely stop scheduling corresponding services for the service data. For example, when the WTRU 2360 discards data 347 to be transmitted to the BS 2370, the WTRU 2360 may completely stop scheduling services for the service data. In another example, when the UPF 2380 discards data 387 for transmission to the BS 2370, the UPF 2380 may completely stop scheduling services for the service data. Similarly, when the BS 2370 discards data 377 for transmission, the BS 2370 may completely stop scheduling services for the service data.

[0168] In step 5, a problem with the first PDU session is detected. In this step, the device or the network detects that there is a problem with the first PDU session and determines to trigger an alternative PDU session to enter the non-discard state. For example, the WTRU 1310 may detect that there is a problem with the first PDU session. Therefore, the WTRU 1310 may then determine to trigger an alternative PDU session to enter the non-discard state. Additionally or alternatively, the BS 1320 may detect that there is a problem with the first PDU session. As a result, the BS 1320 may then determine to trigger an alternative PDU session to enter the non-discard state. Additionally or alternatively, the UPF 1330 may detect that there is a problem with the first PDU session. Therefore, the UPF 1330 may then determine to trigger an alternative PDU session to enter the non-discard state.

[0169] In one example, the WTRU 1310 may be scheduled to transmit a data transfer 352 to the BS 1320, and then the WTRU 1310 may determine to trigger an alternative PDU session. Accordingly, the WTRU 1310 does not transmit the data transfer 352, or does not complete the transmission of the data transfer 352 as scheduled. Additionally or alternatively, the BS 1320 may be scheduled to transmit a data transfer 352 to the WTRU 1310, and the BS 1320 may then determine to trigger an alternative PDU session. As a result, the BS 1320 does not transmit the data transfer 352, or does not complete the transmission of the data transfer 352 as scheduled.

[0170] In an additional or alternative example, the BS 1320 may be scheduled to transmit a data transfer 353 to the UPF 1330, and the BS 1320 may then determine to trigger an alternative PDU session. Accordingly, the BS 1320 does not transmit the data transfer 353, or does not complete the transmission of the data transfer 353 as scheduled. Additionally or alternatively, the UPF 1330 may be scheduled to transmit a data transfer 353 to the BS 1320, and the UPF 1330 may then determine to trigger an alternative PDU session. Accordingly, the UPF 1330 does not transmit the data transfer 353, or does not complete the transmission of the data transfer 353 as scheduled.

[0171] When the device detects a problem with the first PDU session, the detection may be performed by an application hosted in the same device that includes the WTRU 1310 and the WTRU 2360. In one example, the application may be pre-configured. Additionally or alternatively, the application may be configured dynamically.

[0172] In step 6, due to this state transition of the alternative PDU session, the data associated with the alternative PDU session is no longer discarded and is allowed to be transmitted over the air. Data may still be sent and received from the WTRU 1310 to the UPF 1330 via the first PDU session, and the application layer protocol may determine to discard duplicate packets. For example, in step 6, data may be exchanged via the alternative PDU session, such as the WTRU 2360 transmitting a data transfer 367 to the BS 2370, and the BS 2370 then transmitting a data transfer 368 to the UPF 2380. Additionally or alternatively, in one example, when the UPF 2380 transmits a data transfer 368 to the BS 2370, data may be exchanged via the alternative PDU session, and the BS 2370 then transmits a data transfer 367 to the WTRU 2360.

[0173] During the data exchange in step 6, the WTRU 1310 can still transmit data transfer 362 to the BS 1320, and the BS 1320 can in turn transmit data transfer 363 to the UPF 1330. Additionally or alternatively, the UPF 1330 can transmit data transfer 363 to the BS 2320, and the BS 2320 can in turn transmit data transfer 362 to the WTRU 2310. In one example, the application layer protocol can determine that the packet is a duplicate and can determine to discard the packet.

[0174] An example method for improving fault tolerance and reliability is to enhance the WTRU and the network such that the WTRU and the network know when the WTRU and other WTRUs for sending and receiving the same data are hosted in a communication device. The examples and embodiments provided herein clearly describe scenarios where a communication device hosts two WTRUs. However, it can be understood that these solutions can be extended to communication devices that use more than two WTRUs to send and receive the same data.

[0175] Figure 4 is a system diagram showing an example of a communication device having multiple MTs in a system. As shown in the example of system diagram 400, the WTRUs in the device can be independent. In the context of these solutions, independent means that the MT parts of the WTRUs do not communicate directly. In other words, there is no interface between the MT parts of the WTRUs within the communication device. Instead, any coordination between the MTs of each WTRU is done via the application or within the TE.

[0176] For example, in device 402, MT1 441 and MT2 442 may not communicate directly. Instead, any communication or coordination between MT1 441 and MT2 442 can be done through the TE 420. Thus, device 402 can contain independent WTRUs.

[0177] The application can be hosted in the TE part of one WTRU or in the TE common to the two MTs. For example, the application can be hosted in the TE 420.

[0178] In the context of these solutions, independent can also mean that there is no direct communication between the network nodes of the network serving each WTRU; in other words, there is no direct communication to coordinate what data to send to each WTRU. Any network-side coordination can be done via the AS that communicates with the network serving each WTRU.

[0179] For example, MT1441 can communicate with NG-RAN 1414, which in turn can communicate with the operator's 5GC 1406. The operator's 5GC 1406 can communicate with AS 490 over the Nnef 436 link via DN 485. Additionally, MT2442 can communicate with NG-RAN 2415, which in turn can communicate with the operator's 5GC 2407. The operator's 5GC 2407 can communicate with AS 490 over the Nnef437 link via DN 485. Thus, network side coordination can be performed via AS 490. As a result, NG-Ran 1414 may not coordinate with NG-RAN 2415 or the operator's 5GC 2407. Similarly, NG-Ran 2415 may not coordinate with NG-RAN 1414 or the operator's 5GC 1406. Likewise, the operator's 5GC 1406 may not coordinate with the operator's 5GC 2407. In this way, no network side coordination occurs externally via AS 490.

[0180] In the examples provided herein, an alternative PDU session is established and events trigger the WTRU or network node to change the state of the PDU session between a discard state and a non-discard state. In the example, the WTRU and network node can communicate with each other regarding the state change.

[0181] Examples of creating an alternative PDU session are provided here. In one example, the WTRU can initiate the creation of an alternative PDU session. In the embodiments and examples provided herein, an indication can be sent in the indication information.

[0182] Figure 5 is a signaling diagram showing an example of an alternative PDU session initiated by the WTRU. One example in signaling diagram 500 shows the process for configuring an alternative PDU session. This example process is initiated by WTRU 502. This process applies both to alternative PDU sessions and to those with alternative PDU sessions. In other words, both MTs in the WTRU 502 device can perform this process.

[0183] In step 0510, the application hosted in the WTRU 502 device (e.g., in TE 520) determines that an alternative PDU session is needed. The application in the TE part 520 of the WTRU 502 can notify the MT part 540 of the WTRU 502 in the AT command for establishing the PDU session. The application hosted by the WTRU can have information such as configuration information from an application server, which indicates that certain services need to be supported in the alternative PDU session.

[0184] In step 1511, the MT part 540 of the WTRU 502 may indicate to the 5GS that it needs to configure a PDU session with an alternative indication. The WTRU 502 may further indicate whether the PDU session it needs to establish is an alternative or has an alternative. In other words, the WTRU 502 may send an indication of whether the PDU session that the WTRU needs to establish is an alternative PDU session or a primary PDU session. This indication may be sent as indication information.

[0185] In the example, the MT 540 may send this indication to the 5GS in a PDU session establishment request or a PDU session modification request. The MT 540 may send a PDU session establishment request by sending a NAS message to the AMF 582. The AMF 582 may de-encapsulate the message and understand that it is a NAS session management (SM) message. The NAS-MM part of this message may also include an indication of an alternative session, such as an alternative PDU session. This flag may be used by the AMF 582 in SMF selection. For example, if some SMFs do not support the discard / no discard function of the PDU session, the AMF 582 will not select that SMF for the requested PDU session. Then, the AMF forwards the NAS–SM message to the serving / selected SMF, such as the SMF 583.

[0186] In step 2512, the SMF 583 may send an SM policy association request including an alternative indication to the PCF 590. The alternative indication may be included so that the PCF 590 can use the alternative indication to help determine what policy charging and control (PCC) rules to provide to the SMF 583 for the PDU session.

[0187] In step 3513, the PCF 590 may generate / update SM policies related to the PDU session. The SM policies may include one or more of PCC rules, N4 rules for the UPF 584, quality of service (QoS) rules for the WTRU 502, QoS profiles for the RAN node 504, etc. The PCF 590 may decide to include the alternative indication in the rule itself, such as a PCC rule or a QoS rule, rather than sending separate signaling about the alternative indication to the WTRU 502, RAN 504, and UPF 584.

[0188] The alternative indication may indicate that the PDU session is or has an alternative PDU session. The alternative indication may also specify whether it is an alternative session or a PDU session with an alternative.

[0189] This indication may also include the default state of the PDU session, i.e., whether the PDU session and / or network entity should default to a discard state or a no discard state. Depending on pre-configuration or network-assisted inference, the default state may be assigned to the PDU session with MT1, for exampleFigure 4 MT1441 as shown, or the PDU session with MT2, such as MT2442. The alternative indication may include certain triggers or conditions at the network entity level that can cause it to switch to a certain state. Such triggers or conditions may include an indication from the AS or other network entities (e.g., UPF 584, RAN node 504, or WTRU 502) to switch the state of the PDU session, or the fact that network entities such as RAN node 504 or UPF 502 start to exchange data traffic related to this alternative PDU session, as described in the embodiments and examples herein.

[0190] In step 4a 514, the PCF 590 may send an SM policy to the SMF 583 and confirm the association of the SM policy with the alternative indication. In step 4b 515, the SMF 583 may send an alternative PDU session indication to the UPF 584. This alternative PDU session indication may be signaled by the SMF 583 to the UPF 584 via the N4 interface. The indication may also be included as part of the N4 rules that the SMF 583 will send to the UPF 584. The SMF 583 may also use the alternative PDU session indication to perform UPF selection for the PDU session under consideration. The message from the SMF 583 to the UPF 584 may also indicate to the UPF 584 whether the PDU should be placed in a discard state or a non-discard state.

[0191] In step 4c 516, the SMF 583 may send an alternative PDU session indication to the RAN node 504 via an N2 signaling message. In one example, this message may be forwarded by the AMF 582 to the RAN node 504. If the alternative PDU session indication has been added by the PCF 590 to one or more QoS profiles of the RAN node 504, the alternative PDU session indication may also be included in one or more QoS profiles related to the traffic carried in this PDU session. The message from the SMF 583 to the RAN node 504 may also indicate to the RAN node 504 whether the PDU should be placed in a discard state or a non-discard state.

[0192] In step 5517, the SMF 583 may send a PDU session establishment acceptance or PDU session modification command to the WTRU 502 via the AMF 582. In the example of step 5517, this message may be considered a PDU session establishment response message sent from the SMF 583 of the WTRU 502 to the MT540. This message confirms that the PDU session has been successfully established and includes an alternative indication. In one example, this indication may include information about one or more of the following: the state taken, whether the state is a discard state or a non-discard state, or perhaps some condition of a handover state, as described elsewhere herein, for example in step 3513. If the PCF 590 has added an alternative PDU session indication in step 3513, a QoS rule including this indication may be provided to the WTRU.

[0193] Figure 6 is a signaling diagram showing an example of a WTRU-initiated PDU session state change procedure. The example in signaling diagram 600 shows a procedure for configuring dual WTRUs and coordinating the states of their redundant PDU sessions with WTRU assistance. Figure 6 The example shown includes a change in the PDU session state triggered by the WTRU.

[0194] As described above, the WTRU may include a TE part 620 and at least two MTs, such as MT1641 and MT2642. In the example, the MTs do not communicate directly with each other, but the TE 620 may communicate with the two MTs using, for example, AT commands. Additionally, in one example, MT1641 and MT2642 may be in a single device. In another example, MT1641 may be in one device while MT2642 may be in another device.

[0195] An application hosted by the WTRU may be able to detect a need for an alternative PDU session related to some data exchanged between it and the AS through, for example, pre-configuration of an application server. For simplicity, the examples provided herein use 5GC1606 and 5GC2607 as Figure 6 the participants in, without mentioning the 5GC network functions or the network functions involved. However, in the description herein, the examples will describe which network functions are involved in different steps.

[0196] In step 1a 610, the first device or MT1641 is triggered to perform a WTRU-initiated alternative session configuration request procedure with 5GS1606. For example, this procedure may be as in Figure 5be performed as described in the example shown. Prior to this event, the WTRU-hosted application in the TE part 620 of the WTRU detects the need to establish a PDU session with a replacement indication: one PDU session has a replacement indication (associated with MT1641), and one PDU session is a replacement PDU session (associated with MT2642). This replacement indication can be sent as indication information.

[0197] The TE 620 can communicate with the MT1641 via an AT command, as Figure 5 described. For the first PDU session, the replacement indication can be further specified to mean that this is the first PDU session, or the primary PDU session, or a PDU session with a replacement. The process initiated by the WTRU to configure this PDU session also sets the state of this PDU session (terminating at the MT1641) to a non-discarding state. This means that the PDU session and the network element (such as the MT1641) serving or terminating this PDU session also carry the non-discarding state. In one example, the network element serving this PDU session can include one or more of the RAN 1 node 604, 5GC1606, or the UPF1 within 5GC1. Additionally, these network elements can serve the MT1641. In this way, the WTRU can initiate the establishment of a PDU session, alternatively, in a non-discarding state.

[0198] In step 1b 611, the second device or MT2642 is triggered to perform a WTRU-initiated replacement PDU session configuration with the 5GS2607 using the process described in the example shown in Figure 5 . For this PDU session, the replacement indication can be further specified to mean that this is a replacement PDU session. In this way, the WTRU can initiate the establishment of a replacement PDU session in a discarding state.

[0199] Once this process 611 is completed, this PDU session is placed in a discarding state. This also means that the MT2642 and the RAN2 node 605, 5GC2607, and the UPF2 within 5GC2607 serving the MT2642 are also in a discarding state.

[0200] In step 1c 612, once two PDU sessions are successfully established with possibly different networks (such as 5GC1606 and 5GC2607), the WTRU can start sending and receiving data from the 5GC1606, or more precisely, data from the UPF1 within the 5GC1606. Therefore, data can be exchanged on the PDU session as it is in a non-discarding state. Since the replacement PDU session is in a discarding state, the data is discarded within this replacement PDU session and within the MT2642, RAN2 node 605, 5GC2607, and the UPF2 within 5GC2607.

[0201] The example in this scenario takes advantage of the fact that the WTRU-hosted application at TE 620 can detect that a certain session needs to switch its state from a discard state to a non-discard state. First, the WTRU-hosted application can detect whether a PDU session has a problem by the number of data units lost in a certain PDU session. By counting the number of lost data units and a specific threshold, the WTRU-hosted application in TE 620 can determine that there is a problem with a specific PDU session, so that (another) alternative PDU session needs to stop discarding data, which means it needs to switch to a non-discard state. Alternatively, the WTRU application can receive an indication that the PDU session has a problem from the application server and can use this information to decide that the data session needs to switch to a non-discard state.

[0202] The detection by the TE 620 / WTRU-hosted application in TE 620 that there is a problem in the PDU session of interest may reflect different scenarios. For example, a possible network entity failure (such as UPF1 serving the data in MT1641) or a failure of the RAN1 node 604 carrying the service may be reflected in TE 620 detecting that there is a problem with the PDU session. If the conditions (such as QoS parameters or performance) of the first PDU session are not optimal, TE 620 can decide that an alternative PDU session needs to be switched to a non-discard state. In this case, TE 620 can decide that the help of an alternative PDU session is needed.

[0203] This example process provides two options for coordinating the switching of an alternative PDU session to a non-discard state. In Option 1, once the WTRU detects that the alternative PDU session needs to be switched to a non-discard state, as described in detail above, in step 2a 613, the WTRU can send this information / indication to the entities involved so that they know the change in state and they switch their local state to a non-discard state. In one example, the detection that the alternative PDU session needs to be switched to a non-discard state can be performed by the WTRU-hosted application.

[0204] More specifically, in step 2b 614, TE 620 can notify MT2642 that the alternative PDU session needs to be switched to a non-discard state. For example, TE 620 can send indication information to MT2642 indicating that the alternative PDU session needs to be switched to a non-discard state. In one example, TE 620 can use an AT command to send this information. MT2642 can use it to switch the local state of this alternative PDU session to a non-discard state.

[0205] MT2642 can then forward the indication information to service entities, including the UPF2 within the RAN2 node 605 and the 5GC2607 node. MT2642 can send a message dedicated to the RAN2 node 605 via a Radio Resource Control (RRC) signaling message. MT2642 can include in the message the indication information for the RAN2 node 605, indicating that the state of the alternative PDU session has been switched to the no-drop state. The RAN2 node 605 can send a notification of the state change to the AMF, SMF, and UPF. In one example, the AMF, SMF, and UPF may be within the 5GC2607. For example, if the RAN2 node 605 is responsible for discarding data, then for example the UPF may not need to know when the PDU session is in the discard state. In this case, the RAN2 node 605 may not need to notify the UPF. However, if the UPF is responsible for discarding data, then the RAN2 node 605 can send a notification to the UPF that it can stop discarding data. Additionally, this notification can be sent via the GPRS Tunneling Protocol (GTP) signaling and the N3 or N9 interfaces.

[0206] MT2642 can also send a NAS message, such as a PDU session modification request, to the 5GC2607 to indicate that the state of the PDU session needs to be changed. This NAS message can be carried in the RRC message to the RAN2 node 605.

[0207] The AMF2 can forward the message to interested network functions, such as the SMF2. The SMF2 can send the indication to the serving UPF (such as the UPF2), indicating that it needs to switch its state to the no-drop state for the traffic related to the alternative PDU session.

[0208] In step 2c 615, the 5GC2607 can further notify the AS 690 that the data session carried within the 5GC2607 is now in the no-drop state. This indication can be sent to the AS 690 via the NEF notification.

[0209] In option 2, due to receiving the UL data of the PDU session from the WTRU, the network can detect that it is necessary to stop discarding data. The network may realize that it is receiving UL data because the WTRU application tells the WTRU to stop discarding UL data. In this way, MT2642 is able to trigger the network to move the PDU session to the no-drop state so that the WTRU can receive DL data.

[0210] In step 3a 616, the WTRU application can detect that an alternative PDU session needs to switch to the non-discarding state. The WTRU application can decide to send data from the TE 620 to the MT2642. The MT2642 can understand that it needs to stop discarding data for that PDU session and start sending data to the 5GS2607. In step 3a 617, the MT2642 can send UL data to the RAN2 node 605 via the alternative PDU session.

[0211] In step 3b 618, by receiving data related to that PDU session from the MT2642, the RAN2 node 605 can understand or can determine that the alternative PDU session switches its state to the non-discarding state. Additionally, the RAN2605 can start forwarding 619 that data to the serving UPF, such as the UPF2 within the 5GC2607. Thus, the RAN2 node 605 stops discarding data after receiving data for that PDU session. This understanding or this determination of the state can be configured according to the triggering conditions for switching the state. The condition for switching the state to the non-discarding state can be the fact that the PDU session under discussion is in the discarding state. In another example, the condition can be receiving a certain amount of traffic related to that PDU session from the MT2642. In another example, both conditions can be satisfied to trigger the state switch.

[0212] In step 3c 621, due to receiving data related to the alternative PDU session from the RAN2 node 605, the UPF2 within the 5GC2607 can understand or can determine that the PDU session switches to the non-discarding state. This switch can be achieved by configuring the UPF, for example as indicated in the N4 rules, to understand or determine the conditions regarding: a) whether the PDU session state is the discarding state, and b) whether the UPF receives a certain amount of data related to that PDU session from the RAN2 node 605. If one or both conditions are satisfied, the UPF can switch the state to the non-discarding state and start forwarding data to the appropriate DN. Thus, the 5GC2607 can decide to stop discarding data for that PDU session.

[0213] In step 3d 622, the 5GC2607 can notify the AS 690 that the data session is switched to the non-discarding state, for example via a notification from the NEF after subscribing to the state change of the alternative PDU session from the AS 690.

[0214] For both options, once the alternative PDU session is switched to the non-discarding state, in step 4623, the data traffic of that application can now be sent and received between the MT2642 and the UPF2. In this way, data traffic can be exchanged on the alternative PDU session.

[0215] Optionally, data traffic can still be exchanged between the MT1641 and the UPF1. For example, if network conditions degrade the QoE of a PDU session, but the WTRU, the AS 690, or both still want to maintain traffic exchange in this first PDU session, data can still be exchanged between the MT1641 and the UPF1.

[0216] Figure 7 is a signaling diagram showing an example of an AS-initiated alternative PDU session. The example in signaling diagram 700 shows an alternative method for configuring an alternative PDU session, where the process is initiated by an AS (such as AS 760). The AS request can be sent to the 5GS through interaction with the NEF network function. The AS 760 can indicate in this request that the data session has an alternative indication. This indication may mean that the data session or PDU session carrying the session traffic either has or is an alternative PDU session. In this way, the AS 760 can change the PDU session to an alternative PDU session. This indication can be sent as indication information.

[0217] As described above, this configuration process applies to the configuration of alternative or alternative PDU sessions. Elsewhere in this document, it describes how to use this process to provide redundancy for this application data.

[0218] In an initial step, for example step 0710, the WTRU 702 can perform a PDU session establishment process with the 5GS. In one example, the WTRU 702 can establish a PDU session. Specifically, in one example, the WTRU 702 can send a PDU session establishment request message to the SMF 783 via the AMF 782. In this step, no alternative indication or information is provided for this PDU session, and the traffic of the data carried in this PDU session is exchanged as normal between the WTRU 702 and the serving UPF 784.

[0219] At a certain point, e.g., in step 1711, the AS 760 provides service information about application data with an alternative session indication. The AS 760 can provide this information by invoking the NEF API. In one example, the AS 760 can invoke the NEF API for a data session and provide information to the NEF 700 accordingly. For example, the AS 760 can invoke an API similar to the Nnef_AFSessionWithQoS API. In this request, the AS 760 can include one or more of the following: flow description, WTRU IP address, service requirements, QoS reference, QoS parameters, etc. The AS 760 can also include an alternative indication. This alternative indication can mention that the data session has an alternative data session or is an alternative data session. The alternative indication can also include whether the data session (and subsequently the PDU session) and the network entities involved need to be in a discard state or a non-discard state, or which default state the data session needs to be in. This state change can be triggered by an indication from the AS 760 or other wireless communication system entities (e.g., UPF 784, RAN 704, or WTRU 702) to switch the state of the PDU session, or also by the fact that network entities such as the RAN 704 or UPF 784 start exchanging data traffic related to the alternative PDU session, as described elsewhere in this document.

[0220] In step 2712, once the NEF 770 authorizes the AS request, the NEF 770 provides the service information and requirements, including the alternative indication information, to the PCF 790. In one example, the NEF 700 can provide dataset information associated with the alternative indication information to the PCF 790.

[0221] In step 3713, the PCF 790 can use this information to generate PCC rules for the service flow. The PCF 790 can also generate alternative PDU session indication information to notify other network functions. For example, the PCF 790 can generate alternative PDU session indication information. The PCF 790 can generate corresponding N4 rules for the UPF 784, QoS rules for the WTRU 702, and QoS profiles for the RAN node 704. The PCF 790 can include the alternative PDU session indication information in these rules or choose to send the alternative PDU session indication information separately.

[0222] The alternative PDU session indication information can indicate that the PDU session is or has an alternative PDU session. Additionally, the PDU session indication can specify whether it is an alternative session or has an alternative PDU session.

[0223] The alternative PDU session indication information may also include the default state adopted by the PDU session and the entity receiving the indication information. For example, the alternative PDU session indication information may include information specifying whether the PDU session, the network entity, or both should default to a discard state or a non-discard state. Depending on pre-configuration or network-assisted inference, the default state may be assigned to the PDU session with MT1 or the PDU session with MT2. In one example, in Figure 4 , MT1 may be MT1441 and MT2 may be MT2442.

[0224] The alternative PDU session indication information may include certain triggers or conditions at the network entity level that can cause the network entity to switch to a certain state. Such triggers or conditions may include indications to switch the PDU session state from the AS 760 or other wireless communication system entities (e.g., UPF 784, RAN node 704, or WTRU 702). In addition, such triggers or conditions may also include the fact that network entities such as RAN node 704 or UPF 784 start to exchange data traffic related to this alternative PDU session, as described elsewhere in this document.

[0225] In step 4a 714, the PCF 790 sends a PCC rule to the SMF 783, including the alternative PDU session indication information. In step 4b 715, the SMF 783 sends the alternative PDU session indication information to the UPF 784. The alternative PDU session indication information may be signaled by the SMF 783 to the UPF 784. The indication information may also be included as part of the N4 rule that the SMF 783 will send to the UPF784. The SMF 783 may also use the alternative PDU session indication information to perform UPF reselection for the considered PDU session.

[0226] In step 4c 716, the SMF 783 sends the alternative PDU session indication information to the RAN node 705. In one example, the alternative PDU session indication information may be sent via an N2 signaling message. In one example, the message alternative PDU session indication information may be forwarded by the AMF 782 to the RAN node 704. If the PCF 790 has added alternative indication information to the QoS profile sent to the RAN node 704, the alternative PDU session indication information may also be included in the QoS profile related to the traffic carried in this PDU session. Also in step 4c 716, a PDU session modification command may be sent to the WTRU 702, where new QoS parameters and requirements and alternative PDU session indication information may be sent to the WTRU 702. In this way, the PDU session modification process may be performed.

[0227] At the end of step 716, the PDU session has been successfully modified with the alternative PDU session indication information. (For example, the PDU session may have been modified regarding what state to take, such as whether the session is in a discarded state or a non-discarded state. In one example, the PDU session may have been modified based on some conditions to switch states. If the PCF 790 has added the alternative PDU session indication in step 3713, a QoS rule including the indication may be provided to the WTRU 702.)

[0228] Additionally, in step 4d717, the MT part 740 of the WTRU 702 may notify the TE part 720 or an application hosted by the WTRU 702 that the data session for its traffic now has an alternative indication and to which state the PDU session is set. For example, the PDU session may be set to the (discarded) state. In another case, the PDU session is set to the non-discarded state.

[0229] In the above scenario, the PCF 790 may use URSP rules to configure the WTRU 702 with the alternative indication information. In fact, the alternative indication information received by the PCF 790 may trigger the PCF 790 to create, update, or create and update URSP rules for the WTRU 702 to take the alternative indication into account.

[0230] For example, the new URSP rule, the updated URSP rule, or both may have a routing descriptor (RSD) that includes that the PDU session for the traffic matching the traffic descriptor of the URSP rule needs to be an alternative PDU session or have an indication of an alternative PDU session.

[0231] Furthermore, other parameters of the RSD, such as the S-NSSAI value, may be used to determine whether the PDU session is alternative. If a certain S-NSSAI value can indicate that the PDU session established under that S-NSSAI is assumed to be alternative, then the S-NSSAI can be an indicator of whether the PDU session has an alternative nature.

[0232] Once the PCF generates, updates, or generates and updates the URSP rules, it uses the WTRU configuration updater (UCU) to send these URSP rules to the WTRU.

[0233] Figure 8It is a flowchart showing an example of a WTRU supporting an alternative PDU session. As shown in the example in flowchart 800, the WTRU may establish a PDU session with network 810. Specifically, in one example, the WTRU may transmit a request message to establish or modify a PDU session with the network. The WTRU may receive an indication 820 from the network that the PDU session is an alternative PDU session. In one example, the indication may be received as indication information. In addition, the WTRU may determine whether the PDU session is in a discarded state 830. In addition, based on the determination that the PDU session is no longer in a discarded state 850, the WTRU may transmit uplink data associated with the PDU session. In one example, the data may be URLLC data. In additional or alternative examples, the WTRU may detect that the PDU session is no longer in a discarded state.

[0234] In another example, the WTRU may transmit indication information to the network that the PDU session is an alternative PDU session. When the WTRU establishes a PDU session with the network, the WTRU may transmit the indication information. In another example, when the WTRU requests to modify the PDU session, the WTRU may transmit the indication information. The WTRU may transmit the indication information in a PDU session establishment request message. In addition, the WTRU may transmit the indication information in a PDU session modification request message.

[0235] In addition, the WTRU may receive trigger information and may establish a PDU session based on the trigger information. In addition, the WTRU may modify a PDU session based on the trigger information. In addition, the WTRU may make a PDU session an alternative PDU session by applying an AT command that invokes a request to use the alternative PDU session. In addition, the WTRU may make a PDU session an alternative PDU session by detecting that the application traffic matches the traffic descriptor in the URSP rule.

[0236] In another example, the WTRU may receive an indication in a PDU session establishment acceptance message that the PDU session is an alternative PDU session. In another example, the WTRU may receive an indication in a PDU session modification command message that the PDU session is an alternative PDU session.

[0237] In another example, the WTRU may determine that the PDU session is in a discarded state based on the indication in the PDU session establishment acceptance message. In another example, the WTRU may determine that the PDU session is in a discarded state based on the indication in the PDU session modification command message.

[0238] In addition, the WTRU may determine that the PDU session is no longer in a discarded state based on an indication from an application provided in an AT command. In one example, the indication may be provided to the MT portion of the wireless device. In addition, the WTRU may determine that the PDU session is no longer in a discarded state based on receiving downlink data associated with the PDU session. In one example, the downlink data may be URLLC data.

[0239] Figure 9 is a signaling diagram showing an example of a network-initiated PDU session state change procedure. The example in signaling diagram 900 shows the procedure by which the AS 990 may trigger a change in the PDU session state.

[0240] In step 1a 910, the first device or MT1941 is triggered to perform an AS-initiated alternative session configuration procedure, request procedure, or both with the 5GS1906. Prior to this event, the AS 990 provides service information and requirements for different 5GSs through, for example, Figure 9 NEF1 and NEF2 not shown in the figure to configure PDU sessions with alternative indications: one PDU session has an alternative (related to MT1941) and one PDU session is an alternative PDU session (related to MT2942). For the first PDU session, the alternative indication may be further specified to mean that this is the first PDU session, or the primary PDU session, or a PDU session with an alternative. The AS-initiated procedure for configuring this PDU session also sets the state of this PDU session (terminating at MT1941) to a non-discarded state. This means that the PDU session and the network elements (MT1) serving or terminating this PDU session may also carry the non-discarded state. The network elements serving this PDU session may include one or more of the RAN1 node 904, 5GC1906, or the UPF1 within the 5GC1906 serving MT1941. In this way, an AS-initiated PDU session with an alternative can be established in a non-discarded state.

[0241] In step 1b 911, the second device or MT2942 is triggered to perform an AS-initiated alternative PDU session configuration with the 5GS2907. In one example, the second device or MT2942 may use the Figure 7 procedure described in the figure to perform an AS-initiated alternative PDU session configuration. For this PDU session, the alternative indication may be further specified to mean that this is an alternative PDU session.

[0242] Once this process is complete, the PDU session is placed in a discarded state. This also means that MT2942, as well as RAN2 node 905, 5GC2907, and UPF2 within 5GC2907 serving MT2942, are also in a discarded state. In this way, an AS-initiated alternative PDU session can be established in the discarded state.

[0243] In step 1c 912, once two PDU sessions have been successfully established with potentially different networks (e.g., with 5GS1906 and 5GS2907), the WTRU can start sending and receiving data from 5GC1906, or more precisely, data from UPF1 within 5GC1. Thus, data traffic is exchanged on the PDU session.

[0244] Since the alternative PDU session is in a discarded state, within this PDU session, as well as within MT2942, RAN2 node 905, 5GC2907, and UPF2 within 5GC2907, the data is discarded.

[0245] In this example scenario, we use the fact that AS 990 is able to detect that a certain session needs to switch its state from a discarded state to a non-discarded state. For example, such detection can be done by counting the number of lost or data units within this PDU session and potentially using a certain threshold. In another example, if the conditions (e.g., QoS parameters or performance) of the first PDU session are not optimal, such detection can be performed. In this case, AS 990 can decide that the help of an alternative PDU session is needed.

[0246] The examples provided here include two options for coordinating the switch of the alternative PDU session to a non-discarded state. In the example, the first option can be called Option 1, and the second option can be called Option 2.

[0247] In Option 1, once AS 990 detects in step 2a 913 that the alternative PDU session needs to switch to a non-discarded state, AS 990 can send this indication to the 5GS2 entities involved. In one example, this indication can be sent as indication information.

[0248] More specifically, in step 2b 914, AS 990 can notify NEF2 within 5GC2907 that the alternative PDU session needs to switch to a non-discarded state. This session can be identified by an IP 5-tuple or a WTRU ID / DNN / S-NSSAI combination.

[0249] NEF2 can then forward this indication to the serving entities, including PCF2, SMF2, or AMF2. In one example, PCF2, SMF2, or AMF2 can be within 5GC2907.

[0250] The SMF2907 may send this indication to the serving UPF (e.g., UPF2), indicating that it needs to switch its state to a non-discarding state for the traffic related to the alternative PDU session.

[0251] In step 2c 915, the SMF2 may send a NAS message to the MT2942. The SMF2 may include in this message an indication to the RAN2 node 905 that the state of the alternative PDU session has been switched to the non-discarding state. In one example, this indication may be sent as indication information. This message may first be sent to the AMF2 and then forwarded to the RAN2 node 905, and the RAN 2 node 905 may then send it to the MT2942 in an RRC message.

[0252] In Option 2, due to the fact of receiving DL data of the PDU session, the WTRU may detect the need to stop discarding data. The WTRU may recognize that it is receiving DL data because the AS 990 tells the network to stop discarding packets.

[0253] In step 3a 916, the AS 990 may detect that the alternative PDU session needs to be switched to the non-discarding state. Accordingly, the AS 990 decides to send data traffic 917 to the UPF2. In one example, the UPF2 may be within the 5GC2907.

[0254] In step 3b 918, the serving UPF (UPF2) node, due to receiving data related to this PDU session from the AS 990, may understand that the alternative PDU session switches its state to the non-discarding state and starts forwarding this data to the RAN2 node 905. Thus, the 5GC2907 that may include the UPF2 may decide to stop discarding the data of this PDU session. This understanding of the alternative PDU session may be configured according to the triggering conditions for switching the state. The conditions for switching the state to the non-discarding state may include the fact that the PDU session under discussion is in the discarding state. In addition, the conditions for switching the state to the non-discarding state may include receiving a certain amount of traffic related to this PDU session from the AS990. The UPF may send a notification to the SMF to indicate that the PDU session is no longer in the discarding state. Specifically, the UPF2 may send a notification to the SMF2, and both the UPF2 and the SMF2 may be within the 5GC2907. In addition, the 5GC2907 may send DL traffic to the RAN2 node 905 via the alternative PDU session 919.

[0255] Additionally or alternatively, the UPF may be configured with packet detection rules that the UPF may use to detect a specific type of traffic and, when the specific type of traffic is detected, determine to move the PDU session out of the discard state. The SMF may indicate to the UPF which packet detection rules should be used to detect when to move the WTRU out of the discard state. For example, the packet detection rules may be used to detect a series of retransmission attempts, which may indicate a problem with the primary PDU session. In one example, the UPF may be UPF2, the SMF may be SMF2, and both UPF2 and SMF2 may be within 5GC2907.

[0256] In step 3c 920, the RAN2 node 905 may understand that the PDU session is switching to the non-discard state since it receives data related to the alternative PDU session from UPF2. Accordingly, the RAN2 node 905 may stop discarding data. For example, the RAN2 node 905 may determine that the PDU session is switching to the non-discard state based on the condition that the PDU session state is in the discard state and the RAN2 node 905 receives a certain amount of data related to the PDU session from UPF2. If the condition is met, the RAN2 node 905 may switch the state to the non-discard state and start forwarding DL data traffic to the WTRU / MT2942 via the alternative PDU session 921. The UPF may send a notification to the SMF to indicate that the PDU session is no longer in the discard state. The RAN2 node 905 may be configured to make the state determination based on the condition after the condition is indicated by, for example, a condition in the QoS profile.

[0257] In step 3d 922, the MT2942 may understand that the PDU session has switched to the non-discard state since it receives data related to the alternative PDU session from the RAN2 node 905 and may stop discarding data for the PDU session. In one example, the MT2942 may then provide the data to the TE 920, may make the data available to an application in the WTRU, or may do both.

[0258] For option 1 and option 2, once the alternative PDU session has been switched to the non-discard state, in step 4923, data traffic for the application may now be sent and received between the MT2942 and UPF2. Accordingly, the AS 990 and the MT2942 may exchange data traffic over the alternative PDU session. In one example, data traffic may still be exchanged between the MT1941 and UPF1. Additionally, the UPF1 may be within 5GC1906. In one example, network conditions may degrade the QoS of the PDU session, but the WTRU, the AS 990, or both may still want to continue to exchange traffic in both the first PDU session and the alternative PDU session.

[0259] In the example solution above, it can be assumed that the TE 920 communicates with two MTs (MT1 941 and MT2 942), and each MT registers for a PDU session, creates a PDU session, or both, on two different networks. In one example, the two different networks can include 5GC1 and 5GC2 with RAN1 node 904 and RAN2 node 905. It can also be assumed that no communication occurs between the two different networks. As described in the embodiments and examples elsewhere in this document, it is still assumed that the two MTs do not communicate directly with each other.

[0260] Embodiments and examples of dual WTRUs in devices with network coordination are provided herein. The examples herein describe how the networks communicate with each other to coordinate the dual WTRUs for reliability operations described elsewhere in this document. (In addition, the examples herein describe creating alternative PDU sessions, changing the state of alternative PDU sessions, or both.)

[0261] In the example scenario described herein, when there is a service agreement between carriers, communication between network elements of different networks is possible. For example, the service agreement can occur in a mobile phone roaming or WTRU roaming environment.

[0262] In one example, the two networks are able to interact through communication between the PCFs from each network. In addition, in one example, PCF-1 belonging to 5GC1 can be a PCF that is able to receive information and notifications from a PCF that provides policies (such as PCC rules) related to the PDU session. For example, if the policy for a specific PDU session is successfully provided, the PCF can notify PCF-1. PCF-1 can be the contact point between 5GC1 and 5GC2. 5GC2 can host PCF-2, and PCF-2 can communicate with one or more other PCFs related to the PDU session within 5GC2, such as PCC rules. PCF-1 and PCF-2 are different from the PCF that provides alternative indications for the PDU session to ensure that the contact point is not affected if the serving PCF fails. In one example, the contact point can include PCF-1 and PCF-2 between 5GC1 and 5GC2.

[0263] PCF-1 and PCF-2 can communicate with each other via, for example, reference point N24, which is used in a roaming environment and supports communication between the H-PCF and the V-PCF. If N24 is limited to the roaming scenario, PCF-1 and PCF-2 can use a similar interface for communication.

[0264] Figure 10 is a signaling diagram showing an example of a PDU session creation and state change process with network coordination. The example shown in signaling diagram 1000 shows how coordination between networks can be used to assist in PDU session creation and state change.

[0265] In step 11010, a WTRU-initiated procedure for alternative PDU session creation is used to configure an alternative PDU session. In one example, the WTRU-initiated procedure for alternative PDU session creation can be the procedure as seen in the example shown in Figure 5 the example. For example, Figure 5 steps 0 to 5 of the procedure in the example shown in

[0266] can also be used in the example shown here to establish a PDU session in a non-drop state as an alternative. These steps 0 to 5 can be used by one or more of MT21041, RAN 1004, AMF 1082, PCF 1090, SMF 1083, and UPF 1084.

[0267] In step 21011, the PCF 1090 that serves the policies related to session management communicates with PCF-21092, which is the contact point between 5GC2 and 5GC1, to notify PCF-21092 of the successful policy provisioning for certain PDU sessions. The PCF 1090 can indicate an alternative indication related to the alternative PDU session. In addition, this information can include the policy related to this alternative PDU session, as well as the current and default states of the PDU session, such as the drop state of MT21041. The PCF 1090 can also include an ID, which can be used to associate the PDU session with its corresponding session on another network. For example, the PCF 1090 can be an alternative session ID or a DNN / S-NSSAI combination.

[0267] In step 31012, the PCF-21092 in 5GC2 communicates with the PCF-11091 in 5GC1 to notify the PCF-11091 that the policy related to the alternative PDU session has been successfully provided. The PCF-21092 can provide an alternative session ID such that the PCF-11091 can use this ID to identify the corresponding associated PDU session in 5GC1. The PCF-21092 can include the PDU session state, including the default state. Depending on pre-configuration or network-assisted inference, the default state can be assigned to the PDU session of MT11041 or the PDU session of MT2. The PCF-21092 also subscribes to receive notifications related to policy updates, policy changes, or both from the PCF-11091, where the policy updates, policy changes are related to PDU session 1 in 5GC1 and any issues related to this PDU session. For example, these issues may include network entity failures, network congestion, poor network conditions, etc. For example, if the alternative PDU session 1 switches the state from a non-drop state to a drop state, then the PCF-21092 can then receive a notification from the PCF-11091.

[0268] At this stage, due to the coordination of PCF-1 and PCF-2, both alternative PDU sessions are established using information known to each other. The alternative PDU session serving MT1 may be exchanging data because this session may be in a non-discarding state, and the alternative PDU session 1041 serving MT2 may be in a discarding state.

[0269] In step 41013, PCF-1 1091 may detect a problem with the alternative PDU session serving MT1. This may mean that the network function serving this PDU session is faulty. This may also mean that the performance of the PDU session is poor or below a certain level. This may also mean that there is a problem with this PDU session due to network performance issues such as congestion. In this way, PFC-1 1091 can detect that a state change has occurred or a fault has occurred.

[0270] In step 51014, PCF-1 1091 may send a notification to PCF-2 1092 to inform PCF-2 1092 that there is a problem with alternative PDU session 1. Additionally and alternatively, the notification may also inform PCF-2 1092 that the final PDU session state will or can be switched to discarding. In one example, PFC-1 1091 may send the notification via the N24 interface. Additionally, the notification may include information indicating that a problem with the PDU session has been detected.

[0271] In step 61015, after PCF-2 1092 receives the ID of the alternative session that is problematic in 5GS1, PCF-2 1092 may send an indication to the serving PCF 1090, indicating that the PDU session and the serving entity need to switch the state from the discarding state to the non-discarding state. For example, PCF-2 1092 may send an indication to PCF 1090 to switch alternative PDU session 2 to the non-discarding state.

[0272] In step 71016, the alternative PDU session in 5GS2 may switch its state to the non-discarding state together with its serving network entity and MT2 1041. The serving network entities that switch to the non-discarding state may include one or more of UPF 1084, SMF 1083, RAN 1004, and PCF 1090. Data can now be exchanged through this alternative PDU session between the AS and MT2 1041.

[0273] The embodiments and examples provided herein include dual WTRUs in a device with WTRU coordination. In the embodiments and examples provided herein, in addition to communicating with each other via the TE as described in the previous example solutions provided herein, the two MTs residing in the WTRU may also communicate directly with each other through an internal interface.

[0274] Figure 11 It is a signaling diagram showing an example of a PDU session creation and state change process with WTRU coordination. Figure 11 The example shown in shows how WTRU communication can be used to assist in coordinating dual WTRUs for reliable operation. In one example, the WTRU communication can be performed with the MT.

[0275] In steps 1a 1110, 1b 1111, and 1c 1112, similar to Figure 5 , MT11141 and MT21142 respectively establish alternative PDU sessions served by 5GS11106 and 5GS21107. Similarly, the first PDU session in 5GS11106 is placed in a non-discard state, and the alternative PDU session in 5GS21107 is placed in a discard state. At this stage, data related to the service is exchanged between AS1190 and MT11141.

[0276] In step 21113, MT11141 may detect a problem with the first PDU session. For example, if the TE can count data units related to the application service, such as the loss of data units exceeding a specific threshold, the TE can detect a problem with the data session. MT11141 may have received an indication that the PDU session has encountered a problem from the serving RAN1 node 1104 or from 5GC11106. In one example, the problem may be due to feedback from AS 1190 or due to a faulty network element. If MT11141 receives a request from the RAN1 node 1104 or 5GC11106 to switch the PDU session to the discard state, it may detect a problem with the first PDU session. In this way, MT11141 can detect that a state change has occurred or that a fault has occurred.

[0277] In step 3a 1114, MT11141 may convey an indication that the first PDU is problematic or that the first PDU session has switched from a state to a discard state to MT21142.

[0278] In step 3b 1115, MT21115 may infer from the message sent by MT1 in step 3a 1114 that the alternative PDU session needs to switch its state from the discard state to the non-discard state.

[0279] In step 41116, a process similar to the previous embodiments and examples provided herein can be performed to indicate to the network entity and the RAN2 node 1105 that the alternative PDU session needs to switch its state to the non-discard state. The indicated network entity may include one or more of 5GC21107 and AS 1190.

[0280] At this stage, the alternative PDU session state can be switched to the no-drop state and its serving entities. In one example, the serving entities can include the RAN2 node 1105, MT21142, and 5GC functions, such as those performed by 5GC21107. Thus, at step 51117, application data traffic can be exchanged between the AS1190 and the MT21142.

[0281] Although the features and elements have been described above in particular combinations, one of ordinary skill in the art will understand that each feature or element can be used separately or in any combination with other features and elements. Additionally, the methods described herein can be implemented in a computer program, software, or firmware that is included in a computer-readable medium for execution by a computer or processor. Examples of computer-readable media include electronic signals (transmitted via wired or wireless connections) and computer-readable storage media. Examples of computer-readable storage media include, but are not limited to, read-only memory (ROM), random access memory (RAM), registers, cache memory, semiconductor storage devices, magnetic media such as internal hard disks and removable disks, magneto-optical media, and optical media such as CD-ROM disks and digital versatile disks (DVDs). A processor associated with software can be used to implement a radio frequency transceiver that is used for a WTRU, UE, terminal, base station, RNC, STA, AP, relay node, mesh node, customer premise equipment (CPE), fixed wireless access (FWA) device, industrial device, transmit and receive point (TRP), multi-TRP (M-TRP), vehicle, drone, or any host computer.

Claims

1. A method used in a wireless transmit / receive unit (WTRU), the method comprising: Transmitting a request message to establish or modify a protocol data unit (PDU) session with a network, wherein the request message indicates that the PDU session is an alternative PDU session; Receiving, from the network, indication information indicating that the PDU session is an alternative PDU session; Determining, based on the received indication information, whether the PDU session is in a discarded state; And Transmitting uplink data associated with the PDU session based on a determination that the PDU session is no longer in a discarded state.

2. The method according to claim 1, Wherein, The determination that the PDU session is no longer in a discarded state is based on indication information in an attention (AT) command.

3. The method according to claim 2, Wherein, Receiving the indication information in the AT command from an application.

4. The method according to claim 3, Wherein, The application is hosted in the WTRU.

5. The method according to claim 3, Wherein, The application is hosted in the network.

6. The method according to claim 1, wherein the determination that the PDU session is no longer in a discarded state is based on the reception of downlink data.

7. The method according to claim 6, Wherein, The downlink data is associated with the PDU session.

8. The method according to claim 6, Wherein, The downlink data is ultra-reliable low-latency (URLLC) data.

9. The method according to claim 1, Wherein, Receiving, in a PDU session establishment acceptance message, indication information indicating that the PDU session is an alternative PDU session.

10. The method according to claim 1, wherein receiving, in a PDU session modification command message, indication information indicating that the PDU session is an alternative PDU session.

11. A wireless transmit / receive unit (WTRU) comprising: A transceiver; and A processor operably coupled to the transceiver; wherein: The transceiver and the processor are configured to transmit a request message to establish or modify a protocol data unit (PDU) session with a network, wherein the request message indicates that the PDU session is an alternative PDU session; The transceiver is configured to receive, from the network, indication information indicating that the PDU session is an alternative PDU session; The processor is configured to determine, based on the received indication information, whether the PDU session is in a discarded state; And The transceiver and the processor are configured to transmit uplink data associated with the PDU session based on a determination that the PDU session is no longer in a discarded state.

12. The WTRU according to claim 11, wherein the determination that the PDU session is no longer in a discarded state is based on indication information in an attention (AT) command.

13. The WTRU according to claim 12, Wherein, Receiving the indication information in the AT command from an application.

14. The WTRU according to claim 13, Wherein, The application is hosted in the WTRU.

15. The WTRU according to claim 13, Wherein, The application is hosted in the network.

16. The WTRU according to claim 11, wherein the determination that the PDU session is no longer in a discarded state is based on the reception of downlink data.

17. The WTRU according to claim 16, wherein the downlink data is associated with the PDU session.

18. The WTRU according to claim 16, wherein the downlink data is ultra-reliable low-latency (URLLC) data.

19. The WTRU according to claim 11, wherein indication information indicating that the PDU session is an alternative PDU session is received in a PDU session establishment acceptance message.

20. The WTRU according to claim 11, wherein indication information indicating that the PDU session is an alternative PDU session is received in a PDU session modification command message.

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