Managing communications in case of master cell group failure

Abstract

A user equipment (UE) communicates (2002) in dual connectivity (DC) with a master node (MN) and a secondary node (SN). The UE determines (2004) that a radio connection with the MN has failed; transmits (2006), using radio resources of the SN, an indication of the failed radio connection to the SN; detects (2008), after the determining and before the radio connection is resumed, an uplink message transmitted to the MN; and transmits (2010), after the radio connection with the MN is resumed, the uplink message to the MN using radio resources of the MN.

Description

Technical Field

[0001] This disclosure generally relates to wireless communications, and more specifically to managing communications in the event of an MCG failure when a user equipment (UE) is in a dual-connection state with a primary node (MN) and a secondary node (SN). Background Technology

[0002] In some cases, a user equipment (or user equipment, typically abbreviated as "UE") can simultaneously utilize the resources of multiple network nodes (e.g., base stations) interconnected via a backhaul line. When these network nodes support the same radio access technology (RAT) or different RATs, this type of connection is referred to as dual connectivity (DC) or multiple radio DC (MR-DC), respectively. When the UE operates in DC or MR-DC mode, one base station operates as the primary node (MN), while the other base stations operate as secondary nodes (SN). For example, the backhaul line may support the Xn interface.

[0003] The MN can provide control plane and user plane connections to the core network (CN), while the SN typically provides user plane connections but not control plane connections. Cells associated with the MN define primary cell groups (MCGs), and cells associated with the SN define secondary cell groups (SCGs). The UE and base stations (MN and SN) can use signaling radio bearers (SRBs) to exchange radio resource control (RRC) messages and non-access stratum (NAS) messages.

[0004] Several types of SRBs exist that a UE can use when operating in DC mode. SRB1 and SRB2 resources allow the UE and MN to exchange MN-related RRC messages and embed SN-related RRC messages, and can be referred to as MCG SRBs. SRB3 resources allow the UE and SN to exchange SN-related RRC messages and can be referred to as SCG SRBs. Decoupled SRBs allow the UE to directly exchange RRC messages with the MN using the radio resources of the MN, SN, or both. Furthermore, the UE and base station (e.g., MN and SN) use data radio bearers (DRBs) to transmit data on the user plane. A DRB can be an MN-terminated DRB or an SN-terminated DRB. An MN-terminated DRB using only MN low-level resources can be referred to as an MCG DRB, an SN-terminated DRB using only SN low-level resources can be referred to as an SCG DRB, and a DRB using only MN and SN low-level resources can be referred to as a decoupled DRB.

[0005] To further enhance DC operation, the 3GPP organization also proposed a so-called Fast MCG Recovery Procedure. According to this procedure, when a UE operating in DC mode detects an MCG failure, the UE suspends MCG transmissions on all radio bearers and reports the MCG failure to the SN via an MCGFailureInformation message using the SCG branch separated from SRB1 or SRB3. In the case of SRB3, the UE generates a ULInformationTransferMRDC message including the MCGFailureInformation message and transmits it to the SN.

[0006] Then, the SN forwards the MCGFailureInformation message along with the RRC transmission message to the MN, so that the received MCGFailureInformation message notifies the MN of MCG failure. When the SN receives the MCGFailureInformation message, the MN can transmit an RRC reconfiguration message or an RRC release message to the UE using the SCG tributary that separates SRB1 or SRB3. When the UE receives the RRC reconfiguration message, it restarts MCG transmission for all radio bearers. When the UE receives the RRC release message, it releases all radio bearers and configurations.

[0007] Following an MCG failure and when the MCG link becomes unavailable, the UE can initiate a Non-Access Stratum (NAS) procedure to transmit a NAS message. For example, the NAS procedure could be related to emergency services. However, it is unclear how the UE should handle NAS messages after an MCG failure. As a more specific example, it is unclear how the UE can transmit an uplink NAS message and execute the corresponding NAS procedure after an MCG failure.

[0008] Furthermore, when the MN receives an MCGFailureInformation message from the SN, the MN can transmit an RRC reconfiguration message or an RRC release message to the UE using the SCG tributaries of separate SRB1 or SRB3. Upon receiving the RRC reconfiguration message, the UE restarts MCG transmission on all radio bearers. However, when certain processes (e.g., handover) are occurring, the UE may not be able to properly process the RRC reconfiguration message. Additionally, the UE is currently unable to provide measurement reports to the MN, further hindering the MN from properly supporting the handover process. Attached Figure Description

[0009] Figure 1A This is a block diagram of an example system in which the Radio Access Network (RAN) and User Equipment can implement the techniques of this disclosure for managing communications during an MCG failure;

[0010] Figure 1B It is possible Figure 1A A block diagram of an example base station operating in the system, including centralized units (CU) and distributed units (DU);

[0011] Figure 2 yes Figure 1A A block diagram of the example protocol stack upon which the UE communicates with the base station;

[0012] Figure 3 This illustrates an example scenario where the UE initiates a NAS procedure and uses the radio resources of the SCG to transmit an uplink NAS message to the MN when an MCG failure has occurred.

[0013] Figure 4 This illustrates an example scenario where the UE suspends MCG transmission in response to detecting an MCG failure and only resumes MCG transmission after MCG (fast) recovery.

[0014] Figure 5A Showing something similar Figure 4 The example scenario is where the UE detects an MCG failure during RRC reconfiguration;

[0015] Figure 5B Showing something similar Figure 5A An example scenario, but in which the UE ignores (or discards) the RRC reconfiguration in response to detecting an MCG failure;

[0016] Figure 5C Showing something similar Figure 5A or Figure 5B The example scenario, but in which the UE suspends both SCG and MCG transmissions;

[0017] Figure 6A This is a flowchart of an example method in the UE to determine whether the UE should use MCG resources or SCG resources to transmit NAS messages based on whether an MCG failure is detected.

[0018] Figure 6B This is a flowchart of an example method in which the UE determines whether to use the MCG link or the SCG link separated from the SRB to transmit NAS messages based on whether an MCG failure is detected.

[0019] Figure 7A This is a flowchart of an example method in the UE to determine whether the UE should suspend the transmission of NAS messages or use SCG radio resources based on whether MCG fast recovery is enabled and whether an MCG failure is detected;

[0020] Figure 7BThis is a flowchart illustrating an example method in which the UE determines whether to suspend the transmission of NAS messages or use the SCG link with a separate SRB based on whether MCG fast recovery is enabled and whether an MCG failure is detected.

[0021] Figure 8A This is a flowchart illustrating an example method in which the UE determines whether to suspend the transmission of NAS messages or use the SCG link with the separated SRB based on whether SRB2 is a separate SRB and whether an MCG failure is detected.

[0022] Figure 8B This is a flowchart illustrating an example method in which the UE determines whether to suspend the transmission of NAS messages or use the SCG link with the separated SRB based on whether SRB2 is a separate SRB, whether SRB3 is available, and whether an MCG failure is detected.

[0023] Figure 9 The UE determines whether it should restart MCG transmission in response to receiving an RRC reconfiguration from the SN based on the content of the RRC reconfiguration.

[0024] Figure 10A This is a flowchart of an example method in which the UE determines whether it should use SRB1 or SRB3 to transmit measurement report d based on whether an MCG failure is detected.

[0025] Figure 10B This is a flowchart of an example method in which the UE determines whether to use the MCG link or the SCG link separated from the SRB to transmit a measurement report based on whether an MCG failure is detected.

[0026] Figure 11 This is a flowchart illustrating an example method in which the UE determines whether to use SRB1 or SRB3 to transmit a measurement report based on whether the measurement report belongs to MN or SN.

[0027] Figure 12 This is a flowchart of an example method in the MN to determine whether the MN should use the MCG radio resources or communicate NAS messages with the UE via the SN based on whether an MCG failure is detected;

[0028] Figure 13 This is a flowchart of an example method in which the MN determines whether it should use the MCG radio resources or transmit downlink information to the UE based on whether an MCG failure is detected.

[0029] Figure 14 This is a flowchart of an example method in MN for the UE to perform an RRC reconfiguration process after detecting a failure of the UE's MCG;

[0030] Figure 15This is a flowchart of an example method in which the MN determines whether it should use the MCG radio resources or transmit an RRC reconfiguration message to the UE via the SN based on whether an MCG failure is detected.

[0031] Figure 16 This is a flowchart of an example method for forwarding RRC messages received from the UE to the MN in the SN;

[0032] Figure 17A This is a flowchart of an example method in the UE to determine whether the UE should use MCG radio resources or SCG radio resources to transmit a response to a message from the MN based on whether an MCG failure is detected;

[0033] Figure 17B This is a flowchart of an example method in the UE to determine whether the UE should use MCG radio resources or SCG radio resources to transmit a response to a message from the SN based on whether an SCG failure is detected;

[0034] Figure 17C This is a flowchart of an example method in the UE for determining whether the UE should ignore messages received from the MN or SN based on whether an SCG failure is detected;

[0035] Figure 18 This is a flowchart illustrating an example method in which the UE determines whether to ignore an RRC message from the MN or transmit a response to the message based on whether an MCG failure is detected.

[0036] Figure 19 This is a flowchart illustrating an example method in which the UE determines whether to execute an RRC connection re-establishment procedure or indicate the MCG failure to the SN after detecting an MCG failure and depending on whether an RRC reconfiguration procedure initiated by the MN is in progress; and

[0037] Figure 20 This is a flowchart illustrating the method by which the UE determines whether it should transmit an uplink message to the MN after recovering from an MCG failure, based on whether the message was pending when the MCG failure occurred. Summary of the Invention

[0038] The UE disclosed herein can detect MCG failure and, depending on the implementation, transmit an uplink message to the MN using either SCG or MCG resources when uplink NAS or RRC messages are available on the MN. In some cases, the UE transmits the uplink message after MCG recovery and uses MCG resources. In other implementations, for example, the UE uses SCG resources or the SCG tributary of a separate SRB to transmit the uplink message. Furthermore, in various implementations, the UE can determine how to handle the uplink message based on whether MCG fast recovery is enabled, the type of SRB available to the UE (e.g., SRB1, SRB3), and whether an SCG failure has occurred in addition to the MCG failure.

[0039] An example embodiment of these technologies is a method for uplink transmission in a UE communicating with a primary node (MN) and a secondary node (SN) via a DC. The method includes: determining that a radio connection with the MN has failed; transmitting an indication of the failed radio connection to the SN using radio resources of the SN; detecting an uplink message to be transmitted to the MN after determination; and transmitting an uplink message to the MN using radio resources of the MN after the radio connection with the MN has been restored. Detailed Implementation

[0040] Figure 1A An example wireless communication system 100 is depicted, wherein communication devices can implement the communication technologies of this disclosure. The wireless communication system 100 includes a UE 102, a base station 104, a base station 106A, a base station 106B, and a core network (CN) 110. The UE 102 is initially connected to the base station 104.

[0041] Among the other components, EPC 111 may include a Serving Gateway (S-GW) 112 and a Mobility Management Entity (MME) 114. The S-GW 112 is typically configured to transmit user plane packets related to audio calls, video calls, internet services, etc., while the MME 114 is configured to manage authentication, registration, paging, and other related functions. 5GC 160 includes a User Plane Function (UPF) 162, an Access and Mobility Management (AMF) 164, and / or a Session Management Function (SMF) 166. Generally, the UPF 162 is configured to transmit user plane packets related to audio calls, video calls, internet services, etc. The AMF 164 is configured to manage authentication, registration, paging, and other related functions, and the SMF 166 is configured to manage PDU sessions.

[0042] like Figure 1AAs shown, base station 104 supports cell 124, base station 106A supports cell 126A, and base station 106B supports cell 126B. Base station 104 can also support cell 122, and base station 106A can also support cell 128A. Cells 124A and 126A can partially overlap, allowing UE 102 to communicate with base stations 104A and 106A, which operate as primary node (MN) and secondary node (SN), respectively, in DC mode. To directly exchange messages during DC scenarios and other scenarios discussed below, MN 104A and SN 106A can support X2 or Xn interfaces. Typically, CN 110 can connect to any appropriate number of base stations supporting NR cells and / or EUTRA cells.

[0043] In some scenarios, base station 104 performs an immediate (unconditional) SN addition procedure to configure UE 102 to operate in DC mode with base station 104 and base station 106A. Base stations 104 and 106A initially operate as the MN and SN of UE 102, respectively. Later, when UE 102 is in DC mode with MN 104 and S-SN 106A, MN 104 can perform an immediate SN change to change the UE 102's SN from base station 106A (source SN or "S-SN") to base station 106B (target SN or "T-SN").

[0044] In some scenarios, when UE 102 is in DC with MN 104 and SN 106A, UE 102 can detect a primary cell group (MCG) failure, and MN 104 accordingly provides MCG radio resources. In response to this detection, UE 102 can transmit an MCG failure information message to SN 106A via the radio resources of SN 106A (i.e., via secondary cell group (SCG) radio resources). In one implementation, if MN 104 is configured to handle MCG failure information messages, SN 106A can forward the MCG failure information message to MN 104 in an interface message (e.g., an RRC transmission message). In response to receiving the MCG failure information message, MN 104 can send an MCG failure recovery message to UE 102 via SCG radio resources to recover from the MCG failure. In one implementation, MN 104 can send an interface message (e.g., an RRC transmission message) to SN 106A that includes the MCG failure recovery message. SN 106A can allocate SCG radio resources to UE 102. For example, SCG radio resources include one or more physical resource blocks, resource elements, or subcarriers within a time unit. The time unit can be one or more ODFM symbols, time slots, or subframes. UE 102 attempts to recover from an MCG failure based on the MCG failure recovery message.

[0045] Continue to refer to Figure 1ABase station 104 is equipped with processing hardware 130, which may include: one or more general-purpose processors such as a CPU and non-transitory computer-readable memory storing machine-readable instructions executable on the one or more general-purpose processors; and / or dedicated processing units. In an example implementation, processing hardware 130 includes an MN RRC controller 132 configured to manage or control one or more RRC configurations or RRC procedures when base station 104 operates as an MN.

[0046] Base station 106A is equipped with processing hardware 140, which may include: one or more general-purpose processors such as a CPU and non-transitory computer-readable memory storing machine-readable instructions executable on the one or more general-purpose processors; and / or dedicated processing units. In the example implementation, the processing hardware 140 includes: an SN RRC controller 142 configured to manage or control one or more RRC configurations and / or RRC procedures when base station 106A operates as an SN or a candidate SN. Base station 106B may have the same or similar hardware as base station 104 or base station 106A.

[0047] although Figure 1A RRC controllers 132 and 142 are shown to operate as MN and SN, respectively. However, in different scenarios, base stations can typically operate as both MN and / or SN. Therefore, base stations 104, 104A, and 106B can implement a similar set of functions and support both MN and / or SN.

[0048] Still referencing Figure 1A UE 102 is equipped with processing hardware 150, which may include: one or more general-purpose processors such as a CPU and a non-transitory computer-readable memory storing machine-readable instructions executable on the one or more general-purpose processors; and / or dedicated processing units. In an example implementation, processing hardware 150 includes: a UE RRC controller 152 configured to manage or control one or more RRC configurations and / or RRC procedures with RAN 105 (e.g., MN 104A and / or SN 106A).

[0049] More specifically, RRC restart controllers 132, 142, and 152 can implement at least some of the techniques discussed below, referring to the messages and flowcharts, to manage RRC configuration. Although Figure 1A RRC controllers 132 and 142 are presented as separate components; however, in at least some scenarios, base stations 104A and 106A may have similar implementations and operate as MN or SN nodes in different scenarios. In these implementations, base stations 104A and 106A may implement RRC controller 132 and RRC controller 142 to support MN and SN functions, respectively.

[0050] In operation, UE 102 can use radio bearers (e.g., DRB or SRB) terminated at MN 104 or SN 106A in different scenarios. UE 102 can receive radio bearer configuration from MN 104 or SN 106A. When communicating on the radio bearer in the uplink (from UE 102 to the base station) and / or downlink (from the base station to UE 102) directions, UE 102 can apply one or more security keys. In some cases, the UE can use different RATs to communicate with base stations 104 and 106A. Although the examples below specifically involve particular CN types (EPC, 5GC) and RAT types (5G NR and EUTRA), in general, the techniques disclosed herein can also be applied to other suitable radio access and / or core network technologies, such as sixth-generation (6G) radio access and / or 6G core networks or 5G NR-6G DC.

[0051] Figure 1B Example distributed implementations of base stations such as base station 104, 106A, or 106B are depicted. The base station in this implementation may include a centralized unit (CU) 172 and one or more distributed units (DUs) 174. CU 172 is equipped with processing hardware, which may include: one or more general-purpose processors such as a CPU and non-transitory computer-readable memory storing machine-readable instructions executable on the one or more general-purpose processors; and / or dedicated processing units. In one example, CU 172 is equipped with processing hardware 130. In another example, CU 172 is equipped with processing hardware 140. DU 174 is also equipped with processing hardware, which may include: one or more general-purpose processors such as a CPU and non-transitory computer-readable memory storing machine-readable instructions executable on the one or more general-purpose processors; and / or dedicated processing units. In some examples, the processing hardware in the example implementation includes: a Media Access Control (MAC) controller configured to manage or control one or more MAC operations or procedures (e.g., random access procedures); and a Radio Link Control (RLC) controller configured to manage or control one or more RLC operations or procedures when base stations 104, 106A, or 106B operate as MN or SN. The processing hardware may also include: a physical layer controller configured to manage or control one or more physical layer operations or procedures.

[0052] Figure 2An example radio protocol stack 200 is illustrated in a simplified manner, according to which UE 102 can communicate with an eNB / ng-eNB or gNB (e.g., one or more of base stations 104A, 104B, 106A, and 106B). In the example stack 200, the EUTRA physical layer (PHY) 202A provides a transport channel to the EUTRA MAC sublayer 204A, which in turn provides a logical channel to the EUTRA RLC sublayer 206A. The EUTRA RLC sublayer 206A then provides an RLC channel to the EUTRA PDCP sublayer 208, and in some cases, a channel to the NR PDCP sublayer 210. Similarly, the NR PHY 202B provides a transport channel to the NR MAC sublayer 204B, which in turn provides a logical channel to the NR RLC sublayer 206B. The NR RLC sublayer 206B then provides an RLC channel to the NR PDCP sublayer 210. In some implementations, UE 102 supports, for example... Figure 2 The EUTRA and NR stacks shown are designed to support handover between EUTRA and NR base stations and / or support DC on the EUTRA and NR interfaces. Additionally, as... Figure 2 As shown, UE 102 can support the layering of NR PDCP sublayer 210 on EUTRA RLC sublayer 206A.

[0053] EUTRA PDCP sublayer 208 and NR PDCP sublayer 210 receive packets that can be referred to as Service Data Units (SDUs) (e.g., from the Internet Protocol (IP) layer, layered directly or indirectly on PDCP layers 208 or 210), and output packets that can be referred to as Protocol Data Units (PDUs) (e.g., to RLC layers 206A or 206B). Except for the differences between SDUs and PDUs, for simplicity, this disclosure refers to both SDUs and PDUs as “packets”.

[0054] For example, on the control plane, EUTRA PDCP sublayer 208 and NR PDCP sublayer 210 can provide SRBs to exchange RRC messages. On the user plane, EUTRA PDCP sublayer 208 and NR PDCP sublayer 210 can provide DRBs to support data exchange.

[0055] When UE 102 operates in EUTRA / NRDC (EN-DC) mode with base station 104A operating as MeNB and base station 106A operating as SgNB, wireless communication system 100 can provide UE 102 with an MN termination bearer using EUTRA PDCP sublayer 208 or an MN termination bearer using NR PDCP sublayer 210. In various scenarios, wireless communication system 100 can also provide UE 102 with an SN termination bearer using only NR PDCP sublayer 210. The MN termination bearer can be an MCG bearer, an SCG bearer, or a separate bearer. The SN termination bearer can be an MCG bearer, an SCG bearer, or a separate bearer. The MN termination bearer can be an SRB (e.g., SRB1 or SRB2) or a DRB. The SN termination bearer can be an SRB or a DRB.

[0056] Next, refer to Figure 3 and Figure 4 Discussion in Figure 1A Several example scenarios of UE and base station operating in the system managing communication during MCG failure between UE 102 and RAN 105.

[0057] First refer to Figure 3 In scenario 300, base station 104 operates as the MN, and base station 106A operates as the SN. Initially, UE 102 is in 302DC with MN 104 and SN 106A. UE 102 in DC communicates 302UL PDUs and / or DL ​​PDUs with MN 104A and SN 106A. In some implementations, UE 102 in DC may communicate 302UL PDUs and / or DL ​​PDUs via radio bearers that may include SRBs and / or DRBs. MN 104 and / or SN 106A may be configured to the radio bearers of UE 102.

[0058] Later, UE 102 determines 304 MCG failure, such as a radio link failure or reconfiguration failure on the MCG link configured by MN 104. In response to determining 304, UE 102 can execute MCG failure reporting procedure 470, as referenced below. Figure 4As described above. After determining that MCG failure 304 has occurred, UE 102 can initiate a 306 Non-Access Stratum (NAS) procedure. In response to the initiation, UE 102 includes a UL NAS message in the MN UL RRC message and transmits a 308 MN UL RRC message to SN 106A. SN 106A then sends a RAN interface message including the MN UL RRC message to MN 104. Upon receiving the RAN interface message, MN 104 extracts the UL NAS message from the MN UL RRC message and includes the UL NAS message in the RAN-CN interface message. Then, MN 104 sends a 312 RAN-CN interface message to the core network (CN) 110 (e.g., AMF 164 or MME 114).

[0059] Similarly, when UE 102 is in DC with MN 104 and SN 106A, MN 104 can determine that the MCG link between 314 and UE 102 has failed. In some implementations, MN 104 determines the MCG failure because it receives an MCG failure information message in the MCG failure reporting procedure 470. In other implementations, MN 104 determines the MCG failure in response to not receiving a PDU or control signal from UE 102. For example, the PDU could be a MAC, RLC, or PDCP PDU. In another example, the PDU could include an RRC message. UE 102 can transmit control signals on a control channel, which could be, for example, the Physical Uplink Control Channel (PUCCH). In other implementations, MN 104 determines the MCG failure in response to receiving channel state information from UE 102 that provides invalid measurements or indicates poor downlink channel quality, such as below a certain quality threshold. Events 306, 308, 310, and 312 are in Figure 3 This is collectively referred to as UL NAS launch process 350.

[0060] After confirming MCG failure 314, MN 104 can receive RAN-CN interface message 316, which includes a DL NAS message, from CN 110. MN 104 extracts the DL NAS message from the RAN-CN interface message, includes the DL NAS message in the MN DL RRC message, and includes the MN DL RRC message in the RAN interface message. Then, MN 104 sends RAN interface message 318 to SN 106A. SN 106A extracts the MN DL RRC message from the RAN interface message and transmits MN DL RRC message 320 to UE 102. Events 316, 318, and 320 occur in... Figure 3 This is collectively referred to as the DL NAS launch process 360.

[0061] In some implementations, the UL NAS transmission process 350 and the DL NAS transmission process 360 can occur in parallel. In other implementations, the DL NAS transmission process 360 can occur after or before the UL NAS transmission process 350. In some implementations, there may be a dependency between UL NAS messages and DL NAS messages. For example, a DL NAS message may respond to a UL NAS message. In another example, a UL NAS message may respond to a DL NAS message. In other implementations, there may be no dependency between UL NAS messages and DL NAS messages, and these messages may be associated with different corresponding NAS processes.

[0062] In some implementations, the MN UL RRC message for event 308 can be a ULInformationTransfer message, the RAN interface message for event 310 can be an X2 or Xn message, and the RAN-CN interface message for event 312 can be an S1 Application Protocol (S1AP) message or an NG Application Protocol (NGAP) message. The X2 or Xn message can be an RRC transmission message or an SN message (e.g., an SN modification request message). The S1AP or NGAP message can be a UL NAS transmission message. In some implementations, during an MCG failure (in other words, after UE 102 detects a 304 MCG failure and before the UE determines that MCG recovery has been successfully completed), UE 102 can transmit an MN UL RRC message (e.g., a ULInformationTransfer message) to SN 106A on the SCG link (i.e., SCG radio resources or SN radio resources) of a separated SRB (e.g., separated SRB1 or separated SRB2). SN 106A can include the MN UL RRC message in the UE report IE or include the separated SRB IE in the RRC transmission message. In one implementation, UE 102 may, in response to an MCG failure, change the primary path of the separated SRB from "MCG" to "SCG". UE 102 may, in response to an MCG fast recovery procedure such as MCG fast recovery procedure 424, set the primary path from "SCG" to "MCG". In other implementations, during an MCG failure, UE 102 may transmit an MN UL RRC message (e.g., a ULInformationTransfer message) to SN 106A on SRB3. In one implementation, UE 102 may include the MN UL RRC message in an SN UL RRC message (e.g., a UEInformationTransferMRDC message) and transmit the SN UL RRC message to SN 106A on SRB3. SN 106A extracts the MN UL RRC message from the SN UL RRC message. SN 106A can include the MN UL RRC message in the Fast MCG Recovery via SRB3 from SN to MN (RRC transmission message) IE.

[0063] In some implementations, the MN DL RRC message for event 320 can be a DLInformationTransfer message, the RAN interface message for event 318 can be an X2 or Xn message, and the RAN-CN interface message for event 316 can be an S1 Application Protocol (S1AP) message or an NG Application Protocol (NGAP) message. The X2 or Xn message can be an RRC transmission message or an SN message (e.g., a message requiring SN modification). The S1AP or NGAP message can be a DL NAS transmission message. In some implementations, during an MCG failure, MN 104 can send an MN DL RRC message to SN 106A, which in turn transmits the MN DL RRC message to UE 102 on the SCG link (i.e., SCG radio resources or SN radio resources) of the separated SRB (e.g., SRB1 or SRB2). MN 104 can include the MN DL RRC message in the separated SRB IE within the RRC transmission message. In other implementations, during an MCG failure, MN 104 can transmit a RAN interface message including an MN DL RRC message to SN 106A, which in turn transmits the MN DL RRC message to UE 102 on SRB3. MN 104 can include the MN DL RRC message in the Fast MCG Recovery IE from SN to MN via SRB3 in the RRC transmission message. In one implementation, SN 106A can include the MN DL RRC message in an SN DL RRC message (e.g., a DLInformationTransferMRDC message) and transmit the SN DL RRC message to UE 102 on SRB3. UE 102 extracts the MN DL RRC message from the SN DL RRC message.

[0064] In some scenarios or implementations, prior to event 302, MN 104 may send an SN Add Request message to base station 106A to configure base station 106A as the SN of UE 102. In response, SN 106A transmits an SN Add Request Confirmation message to MN 104, including an RRC reconfiguration message. Then, MN 104 transmits an RRC container message, including the RRC reconfiguration message, to UE 102 via MCG radio resources. In response to the RRC container message, UE 102 may transmit an RRC container response message to MN 104 via MCG radio resources. After receiving the RRC container response message, MN 104 may send an SN Reconfiguration Complete message to SN 106A to indicate to SN 106A that UE 102 has successfully received or applied the RRC reconfiguration message. In one implementation, UE 102 may include the RRC reconfiguration complete message in the RRC container message in response to the RRC reconfiguration message, and MN 104 may include the RRC reconfiguration complete message in the SN reconfiguration complete message.

[0065] MN 104 can receive UE capabilities of UE 102 from UE 102 in a UECapabilityInformation message, from another base station (e.g., base station 106B) in a RAN interface message, or from CN 110 in a RAN-CN interface message. UE capabilities indicate that UE 102 is capable of performing MCG fast recovery (i.e., UE 102 is capable of executing MCG failure reporting procedure 470 and MCG failure recovery procedure 424). In some implementations, MN 104 can configure UE 102 to enable MCG fast recovery in an RRC container message because MN 104 determines, based on UE capabilities, that UE 102 supports MCG fast recovery and SN 106A supports MCG fast recovery operation (i.e., as...). Figure 3 , 4As described, SN 106A can forward MN UL RRC messages (received from UE 102) to MN 104 and / or forward MN DL RRC messages (received from MN 104) to UE 102. In some implementations, RAN interface messages can be X2 messages or Xn messages (e.g., handover request messages or UE context retrieval request messages). RAN-CN interface messages can be S1AP messages or NGAP messages (e.g., initial context establishment request messages or handover request messages). In some implementations, SN 106A can indicate support for MCG fast recovery operation in the SN add request confirmation message, allowing MN 104 to determine that SN 106A supports MCG fast recovery operation. In other implementations, MN 104 can determine that SN 106A supports MCG fast recovery operation based on pre-configuration. In other implementations, MN 104 can determine that SN 106A supports MCG fast recovery operation based on indications received from the Operations and Maintenance (O&M) server. Alternatively, MN 104 can configure UE 10 to enable MCG fast recovery in another RRC container message (i.e., a second RRC container message), and transmit the second RRC container message to UE 102 after UE 102 is in DC with MN 104 and SN 106A. In response to the second RRC container message, UE 102 can transmit a second RRC container response message to MN 104.

[0066] According to the example implementation, if MN 104 determines that the UE (e.g., UE 102 or another UE) does not support the MCG fast recovery function or SN 106A does not support the MCG fast recovery operation, then MN 104 does not configure the UE to enable the MCG fast recovery function.

[0067] In some implementations, MN 104 may include at least one radio bearer configuration (e.g., RadioBearerConfig IE) in the RRC container message to configure (i.e., add or modify) one or more radio bearers that may be MN-terminated or SN-terminated bearers. The one or more radio bearers may include DRB, SRB3, split SRB1, and / or split SRB2. The one or more radio bearers may include non-split SRB1 or non-split SRB2, but not split SRB1 or split SRB2. UE 102 configures one or more radio bearers based on at least one radio bearer configuration. In one implementation, MN 104 may receive one of at least one radio bearer configurations from SN 106A in an SN Add Request Acknowledgment message and include that radio bearer configuration in the RRC container message. In another implementation, MN 104 may generate one of the radio bearer configurations and include that radio bearer configuration in the RRC container message. Alternatively, MN 104 may include at least one radio bearer configuration (e.g., RadioBearerConfigIE) in another RRC container message (i.e., a third RRC container message), and transmit the third RRC container message to UE 102 after UE 102 is in DC with MN 104 and SN 106A. In response to the third RRC container message, UE 102 may transmit a third RRC container response message to MN 104. The third RRC container message and the third RRC container response message may be the same as or different from the second RRC container message and the second RRC container response message.

[0068] Upon receiving the RRC reconfiguration message, UE 102 can perform a random access procedure on cell 126A using SN 106A to connect to SN 106A using one or more random access configurations from the RRC reconfiguration. When UE 102 successfully completes the random access procedure on cell 126A, UE 102 at the DC can communicate data (user plane data or control plane data) with MN 104 and SN 106A via MCG radio resources and SCG radio resources through cell 126A. Similarly, when SN 106A identifies UE 102 during the random access procedure, SN 106A can communicate data (user plane data or control plane data) with UE 102 through cell 126A.

[0069] In some implementations, if MN104 is a gNB, the RRC container message and the RRC container response message can be the RRCReconfiguration message and the RRCReconfigurationComplete message, respectively. In other implementations, if MN104 is an eNB or ng-eNB, the RRC container message and the RRC container response message can be the RRCConnectionReconfiguration message and the RRCConnectionReconfigurationComplete message, respectively.

[0070] In some implementations, if SN 106A is a gNB, the RRC reconfiguration message and the RRC reconfiguration complete message can be the RRCReconfiguration message and the RRCReconfigurationcomplete message, respectively. In other implementations, if SN 106A is an eNB or ng-eNB, the RRC reconfiguration message and the RRC reconfiguration complete message can be the RRCConnectionReconfiguration message and the RRCConnectionReconfigurationComplete message, respectively.

[0071] In some implementations, the NAS procedure can be an EPS Mobility Management (EMM) procedure or an EPS Session Management (ESM) procedure, and the UL NAS message can be an EMM or ESM message as specified in 3GPP TS 24.301. In other implementations, the NAS procedure can be a 5G Mobility Management (5GMM) procedure or a 5G Session Management (5GSM) procedure, and the UL NAS message can be a 5GMM or 5GSM message as specified in 3GPP TS 24.501. For example, the UL NAS message can be a Tracking Area Update Request message, a Tracking Area Update Complete message, a Registration Request message, a Registration Complete message, a Service Request message, an Extended Service Request message, a UL NAS Transport message, a UL General NAS Transport message, a Deattach Request message, a Deregistration Request message, an Activate Dedicated EPS Bearer Context Accept message, a Deactivate EPS Bearer Context Accept message, and a PDU Session Modification Complete message.

[0072] In some implementations, DL NAS messages can be EMM or ESM messages as defined in 3GPP TS 24.301. In other implementations, DL NAS messages can be 5GMM or 5GSM messages as defined in 3GPP TS 24.501. For example, DL NAS messages can be Tracking Area Update Acceptance Message, Registration Acceptance Message, Service Acceptance Message, DL NAS Transport Message, DL General NAS Transport Message, Deattach Request Message, Deattach Acceptance Message, Deregistration Request Message, Deregistration Acceptance Message, Activate Dedicated EPS Bearer Context Request Message, Deactivate EPS Bearer Context Request Message, and PDU Session Modification Command Message.

[0073] Now for reference Figure 4 Scenario 400 involves the MCG fast recovery process. In this scenario, base station 104 operates as MN and base station 106A operates as SN. Initially, similar to event 302, UE 102 is in 402DC with MN 104A and SN 106A.

[0074] Later, UE 102 determines that 404MCG has failed (e.g., a radio link failure on the MCG link configured by MN 104). In response to determining 404, UE 102 can suspend 406MCG transmission (i.e., suspend transmission on all MCG links with MN 104) and transmit a 406MCG failure information message to SN 106A, which in turn sends a 406MCG failure information message to MN 104. Events 408 and 410 are in Figure 4 This is collectively referred to as the MCG Failure Reporting Process 470.

[0075] In some implementations, UE 102 may include a first measurement result in the MCG failure information message. UE 102 may perform a measurement (e.g., intra-frequency measurement, inter-frequency measurement, or inter-RAT measurement) according to the first measurement configuration, obtain the first measurement result from the measurement, and include the measurement result in the MCG failure information message. In one implementation, after receiving the first measurement result, MN 104 may perform the 424 MCG failure recovery procedure (described in detail below) with UE 102 via SN 106A to recover from the MCG failure. In some implementations, before the MCG failure (e.g., at event 402), MN 104 may, for example, use the MCG link (i.e., MN radio resources or MCG radio resources) or SRB1 to transmit an RRC reconfiguration message configuring the first measurement configuration to the UE. In response, the UE, for example, uses the MCG link (i.e., MN radio resources or MCG radio resources) or SRB1 to transmit an RRC reconfiguration complete message to MN 104. The first measurement configuration can configure UE 102 to perform intra-frequency measurements, inter-frequency measurements, or inter-RAT measurements. For example, MN 104 can configure UE 102 in the first measurement configuration to perform measurements on a carrier frequency different from the serving carrier frequency of PCell 124. In another example, MN 104 can configure UE 102 in the first measurement configuration to perform measurements on the serving carrier frequency of PCell 124. If MN 104 is a gNB, then MN 104 can configure UE 102 in the first measurement configuration to perform measurements on the EUTRA carrier frequency for inter-RAT measurements. If MN 104 is an eNB or ng-eNB, then MN 104 can configure UE 102 in the first measurement configuration to perform measurements on the NR carrier frequency for inter-RAT measurements. In yet another example, MN 104 can configure UE 102 in the first measurement configuration to perform measurements on the UTRA carrier frequency for inter-RAT measurements. In yet another example, MN 104 can configure UE 102 to perform measurements on the GSM carrier frequency for inter-RAT measurements in the first measurement configuration.

[0076] In some implementations, after receiving the MCG failure information message, MN 104 can send an RRC reconfiguration message 412, including a second measurement configuration (e.g., MeasConfig IE), to SN 106A. SN 106A then sends an RRC reconfiguration message 414 to UE 102. In response, UE 102 can send an RRC reconfiguration complete message 416 to SN 106A, which then sends an RRC reconfiguration complete message 418 to MN 104. The second measurement configuration can configure UE 102 to perform intra-frequency measurements, inter-frequency measurements, or inter-RAT measurements. For example, MN 104 can configure UE 102 to perform measurements on a carrier frequency different from the serving carrier frequency of PCell 124 in the second measurement configuration. In another example, MN 104 can configure UE 102 to perform measurements on the serving carrier frequency of PCell 124 in the second measurement configuration. If MN 104 is a gNB, then MN 104 can configure UE 102 to perform measurements for inter-RAT measurements on the EUTRA carrier frequency in the second measurement configuration. If MN 104 is an eNB or ng-eNB, then MN 104 can configure UE 102 to perform measurements for inter-RAT measurements on the NR carrier frequency in the second measurement configuration. In yet another example, MN 104 can configure UE 102 to perform measurements for inter-RAT measurements on the UTRA carrier frequency in the second measurement configuration. In yet another example, MN 104 can configure UE 102 to perform measurements for inter-RAT measurements on the GSM carrier frequency in the second measurement configuration. Events 412, 414, 416, and 418 are... Figure 4 This is collectively referred to as Measurement Configuration Procedure 472. In response to Measurement Configuration Procedure 472, UE 102 does not restart MCG transmission.

[0077] MN 104 can be configured with a first measurement configuration and a second measurement configuration for different mobility management purposes. In some implementations, MN 104 can configure the UE to perform intra-frequency or inter-frequency measurements in the first measurement configuration and to perform inter-RAT measurements in the second measurement configuration. In other implementations, MN 104 can configure the UE to perform intra-frequency measurements in the first measurement configuration and to perform inter-frequency measurements in the second measurement configuration. In still other implementations, MN 104 can configure the UE to perform intra-frequency / inter-frequency RAT measurements in both the first and second measurement configurations, which are configured with different measurement carrier frequencies or different reporting configurations.

[0078] In some implementations, in response to receiving a RAN-CN interface (e.g., S1 or NG) message for UE 102 from CN 110 (e.g., AMF 164 or MME 114), MN 104 can perform measurement configuration procedure 472 with UE 102 via SN 106A. For example, the RAN-CN interface message can instruct MN 104 to move UE 102 to a legacy RAT network for a fallback procedure. CN 110 indicates a CS fallback to MN 104 in a RAN-CN interface message (e.g., a UE context modification request message), allowing MN 104 to configure UE 102 to measure GSM or UTRA carrier frequencies in a second measurement configuration in response to the CS fallback instruction. In another example, CN 110 requests resources (e.g., QoS flow) for IMS voice call establishment in a RAN-CN interface message (e.g., a PDU session resource modification request message), and MN 104 does not support IMS voice. Because MN 104 does not support IMS voice, in response to an EPS fallback instruction, MN 104 can configure UE 102 to perform measurements on the EUTRA carrier frequency in the second measurement configuration. In other implementations, MN 104 can transmit the second measurement configuration in response to receiving a first UL NAS message or an MN UL RRC message including a second UL NAS message from UE 120. The second UL NAS message may be the same as or different from the first NAS message. For example, the first UL NAS message may be a service request message or an extended service request message, and the MN ULRRC message may be a ULInformationTransfer message. If MN 104 receives an MN ULRRC message that does not include a NAS message, then MN 104 may not perform measurement configuration procedure 472.

[0079] In other implementations, in response to receiving an MCG failure information message, MN 104 may perform measurement configuration procedure 472 with UE 102 via SN 106A. For example, MN 104 may not find a suitable cell for UE 102 in the first measurement result in the MCG failure information message, causing MN 104 to perform measurement configuration 472.

[0080] After receiving the MCG failure message, UE 102 can send a 420 First Measurement Report Message (420) to SN 106A for MN 104, and SN 106A then sends a 422 First Measurement Report Message (422) to MN 104. Events 420 and 422... Figure 4 This is collectively referred to as Measurement Reporting Process 474.

[0081] In some implementations, UE 102 may perform a measurement based on a first measurement configuration or a second measurement configuration, obtain a second measurement result from the measurement, and include the second measurement result in a first measurement report message. In other implementations, UE 102 may perform a measurement based on a first measurement configuration or a second measurement configuration, obtain a third measurement result from the measurement, and include the third measurement result in a second measurement report message. UE 102 may then execute measurement reporting procedure 474 again to transmit a second measurement report message to MN 104. In some implementations, if the first measurement result indicates that a cell is suitable for UE 102 to recover from MCG failure on that cell, MN 104 may execute an MCG failure recovery procedure in response to an MCG failure information message. In other implementations, if the first measurement result indicates that no cell is suitable for UE 102 to recover from MCG failure, MN 104 may not execute an MCG failure recovery procedure in response to an MCG failure information message. After receiving the second / third measurement result, if the second / third measurement result indicates that the cell is suitable for UE 102 to recover from MCG failure on that cell, then MN 104 can perform the 424 MCG failure recovery procedure with UE 102 via SN 106A to recover from the MCG failure. In some implementations, in response to an MCG failure, UE 102 can start a timer (e.g., T316). If the timer expires, UE 102 can perform an RRC connection re-establishment procedure. If UE 102 recovers from the MCG failure in response to the MCG failure recovery procedure, then UE 102 stops the timer.

[0082] To perform the MCG failure recovery procedure, MN 104 can send an MCG failure recovery message to SN 106A, which in turn sends an MCG failure recovery message to UE 102. In response to the MCG failure recovery procedure or based on the MCG failure recovery message, UE 102 can resume 426 MCG transmission. After UE 102 restarts MCG transmission, UE 102 suppresses the transmission of MNUL RRC messages to SN 106A. In some implementations, during an MCG failure, UE 102 can transmit an SN ULRRC message (e.g., a measurement report message) to SN 106A on SRB3.

[0083] In some implementations, the MCG failure recovery message can be a MobilityFrom "source RAT" Command message (a mobility command from the "source RAT") for inter-RAT handover to the target RAT. The source RAT is different from the target RAT. When the first / second / third measurement results indicate that the cell is suitable, MN 104 can prepare to hand over to the cell of the target RAT of UE 102. During preparation, MN 104 can obtain the target handover command message for handover to the cell of the target RAT from the base station of the target RAT via the RAN interface (e.g., Xn) or RAN-CN interface (e.g., S1 or NG). Then, MN 104 sends the MobilityFrom "source RAT" Command message including the target handover command message to SN 106A, and SN 106A then sends the MobilityFrom "source RAT" Command message to UE 102. After sending the MobilityFrom "source RAT" Command to SN 106A, MN 104 can perform an SN release procedure and / or a context release procedure with SN 106A. In some implementations, MN 104 may perform an SN release procedure and / or a context release procedure with SN 106A some time after sending the MobilityFrom “source RAT” Command message to SN 106A. In other implementations, MN 104 may perform an SN release procedure and / or a context release procedure with SN 106A after receiving a RAN interface message (e.g., an RRC transmission message) from SN 106A indicating that the MobilityFrom “source RAT” Command message has been transmitted to UE 102.

[0084] UE 102 can perform a handover to the cell of the target RAT according to the target handover command message, and in response to the target handover command message, transmit a target handover completion message on the cell of the target RAT.

[0085] In some implementations, the source RAT can be EUTRA, and the MobilityFrom"source RAT"Command can be a MobilityFromEUTRACommand message. If the target RAT is NR, the target handover command message and the target handover completion message can be RRCReconfiguration and RRCReconfigurationComplete messages, respectively. If the target RAT is UTRA, the target handover command message and the target handover completion message can be HandoverToUTRANCommand and HandoverToUTRANComplete messages, respectively. If the target RAT is GSM, the target handover command message and the target handover completion message can be a handover command message and a handover completion message, respectively. If one of the source RAT and the target RAT is EUTRA / EPC and the other is EUTRA / 5GC, the target handover command message and the target handover completion message can be RRCConnectionReconfiguration and RRCConnectionReconfigurationComplete messages, respectively.

[0086] In other implementations, the source RAT can be NRm, and the MobilityFrom"source RAT"Command can be a MobilityFromNRCommand message. If the target RAT is ETURA, the target handover command message and the target handover completion message can be RRCConnectionReconfiguration and RRCConnectionReconfigurationComplete messages, respectively. If the target RAT is UTRA, the target handover command message and the target handover completion message can be HandoverToUTRANCommand and HandoverToUTRANComplete messages, respectively.

[0087] If MN 104 is the primary eNB (MeNB) or primary ng-eNB (Mng-eNB), the MCG failure recovery message can be an RRCConnectionReconfiguration message, which includes a MobilityControlInfo IE for intra-system handover to the EUTRA cell. In some implementations, MN 104 can prepare UE 102 for handover to the EUTRA cell when the first / second / third measurement results indicate that the EUTRA cell is suitable. As part of the preparation, MN 104 can generate an RRCConnectionReconfiguration message or obtain an RRCConnectionReconfiguration message from the target base station (i.e., the eNB or ng-eNB). MN 104 then transmits the RRCConnectionReconfiguration message to SN 106A, which in turn transmits an RRCConnectionReconfiguration message to UE 102. After receiving the RRCConnectionReconfiguration message, UE 102 can restart MCG transmission on the EUTRA cell. UE 102 performs a handover to the EUTRA cell based on the RRCConnectionReconfiguration message and, in response to the RRCConnectionReconfiguration message, transmits an RRCConnectionReconfigurationComplete message on the EUTRA cell. After the handover to the EUTRA cell, UE 102 transmits an MN UL RRC message on the EUTRA cell instead of transmitting it to SN 106A.

[0088] In some implementations, MN 104 or the target base station may indicate the release of SN 106A in the RRCConnectionReconfiguration message. After sending the RRCConnectionReconfiguration message to SN 106A, MN 104 may perform an SN release procedure and / or a context release procedure with SN 106A. In some implementations, MN 104 may perform the SN release procedure and / or a context release procedure with SN 106A some time after sending the RRCConnectionReconfiguration message to SN 106A. In other implementations, MN 104 may perform the SN release procedure and / or a context release procedure with SN 106A after receiving a RAN interface message (e.g., an RRC transmission message) from SN 106A indicating that the RRCConnectionReconfiguration message has been transmitted to UE 102.

[0089] If MN 104 is the primary eNB (MeNB) or primary ng-eNB (Mng-eNB), the MCG failure recovery message can be an RRCConnectionRelease message that redirects UE 102 to an EUTRA cell or a target RAT cell. In the RRCConnectionRelease message, MN 104 can instruct UE 102 to enter an idle or inactive state and redirect UE 102 to a specific cell and / or a specific carrier frequency. MN 104 can determine the specific cell and / or specific carrier frequency based on first / second / third measurement results. The specific carrier frequency can be an EUTRA, NR, UTRA, or GSM carrier frequency, which can be indicated in the second / third measurement results. The specific cell can be an NR cell, EUTRA cell, UTRA cell, or GSM cell, which can be indicated in the second / third measurement results. UE 102 transitions to an idle or inactive state and selects a specific cell or a specific cell on a specific carrier frequency according to the RRCConnectionRelease message.

[0090] If MN 104 is the primary gNB (MgNB), the MCG failure recovery message can be an RRCReconfiguration message including a ReconfigurationWithSync IE for handover to the NR cell. In some implementations, MgNB 104 can prepare UE 102 for handover to the NR cell when the first / second / third measurement results indicate that the NR cell is suitable. During preparation, MgNB 104 can generate an RRCReconfiguration message or obtain an RRCReconfiguration message from the target gNB. MgNB 104 then transmits the RRCReconfiguration message to SN 106A, which in turn transmits the RRCReconfiguration message to UE 102. UE 102 can restart MCG transmission on the NR cell after receiving the RRCReconfiguration message. UE 102 performs the handover to the NR cell based on the RRCReconfiguration message and transmits an RRCReconfigurationComplete message on the NR cell in response to the RRCReconfiguration message. After switching to the NR cell, UE 102 transmits the MN ULRRC message on the NR cell instead of to SN 106A.

[0091] In some implementations, MgNB 104 or the target gNB may indicate the release of SN106A in the RRCReconfiguration message. MN 104 may perform an SN release procedure and / or a context release procedure with SN 106A after sending the RRCReconfiguration message to SN 106A. In some implementations, MgNB 104 may perform an SN release procedure and / or a context release procedure with SN 106A some time after sending the RCReconfiguration message to SN 106A. In other implementations, MgNB 104 may perform an SN release procedure and / or a context release procedure with SN 106A after receiving a RAN interface message (e.g., an RRC transmission message) from SN 106A indicating that an RRC configuration message has been transmitted to UE 102.

[0092] If MN 104 is a MgNB, the MCG failure recovery message can be an RRCRelease message that redirects UE 102 to an NR cell or a target RAT cell. In the RRCRelease message, MgNB 104 can instruct UE 102 to enter an idle or inactive state and redirect UE 102 to a specific cell and / or a specific carrier frequency. MgNB 104 can determine the specific cell and / or specific carrier frequency based on first / second / third measurement results. The specific carrier frequency can be an EUTRA, NR, or UTRA carrier frequency, which can be indicated in the first / second / third measurement results. The specific cell can be an NR cell, EUTRA cell, or UTRA cell, which can be indicated in the second / third measurement results. UE 102 transitions to an idle or inactive state and selects a specific cell or a specific cell on a specific carrier frequency according to the RRCRelease message.

[0093] In some implementations, during an MCG failure, UE 102 may transmit MN UL RRC messages (e.g., MCG failure information messages, RRC reconfiguration completion messages, and / or measurement report messages) to SN 106A on the SCG link (i.e., SCG radio resources or SN radio resources) of the separated SRB1. For each MN UL RRC message, SN 106A may send a RAN interface message including the MN UL RRC message to MN 104. For example, the RAN interface message may be an RRC transmission message, and SN 106A may include the MN UL RRC message in the UE report IE, or include the separated SRB IE in the RRC transmission message. In one implementation, in response to an MCG failure, UE 102 may change the primary path of the separated SRB1 from "MCG" to "SCG". In response to an MCG fast recovery procedure similar to MCG fast recovery procedure 424, UE 102 may change the primary path of the separated SRB1 from "SCG" to "MCG". In other implementations, during an MCG failure, UE 102 may transmit an MN UL RRC message (e.g., an MCG failure information message, an RRC reconfiguration completion message, and / or a measurement report message) to SN 106A on SRB3. In one implementation, UE 102 may include the MN UL RRC message in an SN UL RRC message (e.g., a UEInformationTransferMRDC message) and transmit the SN UL RRC message to SN 106A on SRB3. SN 106A extracts the MN UL RRC message from the SN UL RRC message. For each MN UL RRC message, SN 106A may send a RAN interface message including the MN UL RRC message to MN 104. For example, the RAN interface message may be an RRC transfer message, and SN 106A may include the MN UL RRC message in the Fast MCG Recovery IE from SN to MN via SRB3 within the RRC transfer message.

[0094] In some implementations, during an MCG failure, MN 104 may send each of the following MN DL RRC messages (e.g., RRC reconfiguration messages and / or MCG fast recovery messages) to SN 106A, which in turn transmits the MN DL RRC message to UE 102 on the SCG link (i.e., SCG radio resources or SN radio resources) of the separated SRB1. For each MN DL RRC message, MN 104 may send a RAN interface message including the MN DL RRC message to SN 106A. For example, the RAN interface message may be an RRC delivery message, and MN 104 may include the MN DL RRC message in the separated SRB IE of the RRC delivery message. In other implementations, during an MCG failure, for each MN DL RRC message, MN 104 may send a RAN interface message including the MN DL RRC message to SN 106A, which in turn transmits the MN DL RRC message to UE 102 on SRB3. For example, the RAN interface message can be an RRC transmission message, and MN 104 can include the MN UL RRC message in the Fast MCG Recovery IE from SN to MN via SRB3 in the RRC transmission message. In one implementation, SN 106A can include the MN DL RRC message in the SN DL RRC message (e.g., the DLInformationTransferMRDC message) and transmit the SN DL RRC message to UE 102 on SRB3. UE 102 extracts the MN DL RRC message from the SN DL RRC message.

[0095] In some implementations, if UE 102 initiates a NAS procedure during an MCG failure (i.e., similar to event 306 before the MCG failure recovery procedure), UE 102 may perform a UL NAS transmission procedure similar to UL NAS transmission procedure 350 to transmit a UL NAS message of the NAS procedure to MN 104. In other implementations, if UE 102 initiates a NAS procedure during an MCG failure (i.e., similar to event 306 before the MCG failure recovery procedure), UE 102 does not perform a UL NAS transmission procedure similar to UL NAS transmission procedure 350. During an MCG failure, UE 102 suppresses the transmission of UL NAS messages of the NAS procedure. After UE 102 recovers from the MCG failure through MCG failure recovery procedure 424, UE 102 may transmit a UL NAS message. More specifically, if / after UE 102 responds to an MCG failure recovery procedure by switching or redirecting to a cell of MN 104 (e.g., cell 122 or 124), UE 102 may transmit a UL NAS message to MN 104 on that cell. If / after UE 102 responds to an MCG failure recovery procedure by switching or redirecting to a target base station's cell (e.g., cell 122 or 124) and the target base station and MN 104 are of the same type (i.e., eNB, ng-eNB, or gNB), UE 102 may transmit a UL NAS message to the target base station on that cell. Otherwise, UE 102 may abort the NAS procedure or abort the transmission of the UL NAS message. In some implementations, if UE 102 is unable to transmit a UL NAS message during an MCG failure, the RRC layer of UE 102 may notify upper layers (e.g., EMM layer, 5GMM layer, ESM layer, and / or 5GSM layer) of the failure to deliver the UL NAS message. After the transmission duration, the upper layer can resubmit the UL NAS message to the RRC layer.

[0096] In some implementations, if MN 104 receives a DL NAS message for UE 102 during an MCG failure (i.e., similar to event 306 before the MCG failure recovery process), MN 104 may perform a DL NAS transmission procedure similar to DL NAS transmission procedure 360 ​​to transmit the DL NAS message of the NAS procedure to UE 102. In other implementations, if MN 104 receives a DL NAS message for UE 102 during an MCG failure (i.e., similar to event 306 before the MCG failure recovery process), MN 104 does not perform a DL NAS transmission procedure similar to DL NAS transmission procedure 360. In one implementation, MN 104 suppresses the transmission of DL NAS messages while the MCG failure condition persists. After MN 104 recovers from the MCG failure through MCG failure recovery procedure 424, MN 104 may transmit DL NAS messages. More specifically, if / after UE 102 switches or redirects to a cell of MN 104 (e.g., cell 122 or 124) in response to an MCG failure recovery procedure, MN 104 may transmit DL NAS messages to MN 104 on that cell. Otherwise (e.g., if MN 104 determines to switch or redirect UE 102 to a cell of the target base station (e.g., cell 122 or 124)), MN 104 may abort or suspend the transmission of DL NAS messages and / or discard DL NAS messages. In the case of abortion or discard, MN 104 may send a RAN-CN interface message (e.g., NAS not delivered indication message) to CN 110 to indicate that MN 104 has failed or has not started transmitting DL NAS messages to UE 102. In another implementation, if MN 104 receives a DL NAS message during an MCG failure (i.e., similar to event 306 prior to the MCG failure recovery process), MN 104 may abort or suspend the transmission of the DL NAS message and / or discard the DL NAS message. In this implementation, MN 104 may send a RAN-CN interface message (e.g., a NAS not delivered indication message) to CN 110 to indicate that MN 104 has failed or has not started transmitting DLNAS messages to UE 102.

[0097] In some implementations, if UE 102 has a UL NAS message to transmit when it determines that 404MCG has failed, UE 102 may include the UL NAS message in the MCG failure information message. In other implementations, if UE 102 has a UL NAS message to transmit during the MCG failure, in response to the MCG failure recovery message, UE 102 may include the UL NAS message in the RRC reconfiguration complete message 416, measurement report message 420, or MCG failure recovery complete message (e.g., RRCReconfigurationComplete message or RRCConnectionReconfigurationComplete message) of the MCG failure recovery procedure 424. When MN 104 receives the UL NAS message from UE 102, MN 104 may forward the UL NAS message to CN 110, as in event 312. In some implementations, if MN 104 receives a DL NAS message from CN 110 during an MCG failure, MN 104 may include the DL NAS message in the RRC reconfiguration message 412 or the MCG failure recovery message in the MCG failure recovery procedure 424. Therefore, UE 102 may receive the DL NAS message upon receiving the RRC reconfiguration message 412 or the MCG failure recovery message.

[0098] In some implementations, if SN 106A is a gNB, the RRC reconfiguration message and the RRC reconfiguration complete message can be the RRCReconfiguration message and the RRCReconfigurationComplete message, respectively. In other implementations, if SN 106A is an eNB or ng-eNB, the RRC reconfiguration message and the RRC reconfiguration complete message can be the RRCConnectionReconfiguration message and the RRCConnectionReconfigurationComplete message, respectively.

[0099] Next reference Figure 5A Scenario 500A also involves the MCG fast recovery process. In this scenario, base station 104 operates as the MN and base station 106A operates as the SN. Events 502A, 504A, 506A, 570A, 516A, 518A, 524A, and 526A are similar to events 402, 404, 406, 470, 416, 418, 424, and 426. The following describes... Figure 5A and Figure 4 The differences between them.

[0100] MN 104 generates an RRC reconfiguration message (i.e., the MN RRC message) that includes the configuration for UE 102. Then, when the UE is in DC with MN 104 and SN 106A, MN 104 transmits a 503RRC reconfiguration message to UE 102. When UE 102 receives the 503A RRC reconfiguration message, UE 102 determines that the 504A MCG has failed. In response to the MCG failure, UE 102 suspends the transmission of the 506AMCG, preventing UE 102 from using the MCG radio resources to transmit an RRC reconfiguration complete message to MN 104 in response to the RRC reconfiguration message. Instead, UE 102 transmits a 516A RRC reconfiguration complete message to SN 106A, which in turn sends a 518A RRC reconfiguration complete message to MN 104. Upon receiving the RRC reconfiguration complete message, MN 104 can determine that UE 102 has received the RRC reconfiguration message 503A and applied the configuration. Therefore, configuration inconsistencies between UE102 and MN 104 can be avoided. In some implementations, UE 102 can transmit the RRC reconfiguration complete message 516A after transmitting the MCG failure information message. In other implementations, UE 102 can transmit the RRC reconfiguration complete message 516A before transmitting the MCG failure information message.

[0101] In some implementations, if MN 104 is a gNB, the RRC reconfiguration message and the RRC reconfiguration complete message can be the RRCReconfiguration message and the RRCReconfigurationComplete message, respectively. In other implementations, if MN 104 is an eNB or ng-eNB, the RRC reconfiguration message and the RRC reconfiguration complete message can be the RRCConnectionReconfiguration message and the RRCConnectionReconfigurationComplete message, respectively.

[0102] In some implementations, UE 102 may include an indication in the MCG failure information message to indicate to MN 104 that UE 102 has received an RRC reconfiguration message. In such an implementation, UE 102 does not transmit the RRC reconfiguration message 516A.

[0103] Next reference Figure 5B Similar to Figure 5AScenario 500B involves the MCG fast recovery process. In this scenario, base station 104 operates as the MN and base station 106A operates as the SN. Events 502B, 504B, 506B, 570B, 524B, and 526B are similar to events 402, 404, 406, 470, 416, 418, 424, and 426. The following describes... Figure 5B , Figure 5A and Figure 4 The differences between them.

[0104] MN 104 generates an RRC reconfiguration message (i.e., the MN RRC message) that includes the first configuration for UE 102. Then, when the UE is in DC with MN 104 and SN 106A, MN 104 transmits a 503B RRC reconfiguration message to UE 102. When UE 102 receives the 503B RRC reconfiguration message, UE 102 determines that the 504B MCG has failed. In response to the MCG failure, UE 102 suspends the transmission of the 506B MCG and ignores (or discards) the 508B RRC reconfiguration message. That is, UE 102 does not apply the first configuration in the RRC reconfiguration message. Event 506B can occur before or after event 508B. When an MCG failure information message is received from UE 102 via SN 106A, MN 104 can determine that UE 102 has not applied the first configuration in the RRC reconfiguration message. Therefore, inconsistencies in configuration between UE 102 and MN 104 can be avoided.

[0105] In some implementations, similar to events 412, 414, 416, and 418, MN 104 may transmit another RRC reconfiguration message (a second RRC reconfiguration message) including the first configuration to UE 102 via SN 106A during an MCG failure, and UE 102, in response to the second RRC reconfiguration message, transmits another RRC reconfiguration completion message (a second RRC reconfiguration completion message) to MN 104 via SN. In other implementations, MN 104 may include the first configuration in the MCG fast recovery message during MCG fast recovery procedure 524. In yet another implementation, after MCG fast recovery procedure 524, MN 104 may use MCG radio resources to transmit a third RRC reconfiguration message including the first configuration to UE 102, and UE 102, in response to the third RRC reconfiguration completion message, uses MCG radio resources to transmit a third RRC reconfiguration completion message to MN 104.

[0106] Next reference Figure 5C Similar to Figure 5AScenario 500C involves the MCG fast recovery process. In this scenario, base station 104 operates as the MN and base station 106A operates as the SN. Events 502C, 504C, and 506C are similar to events 402A, 404A, and 406A. The following describes... Figure 5C , Figure 5A and Figure 4 The differences between them.

[0107] MN 104 generates an RRC reconfiguration message (i.e., the MN RRC message) that includes the first configuration for UE 102. Then, when the UE is in DC with MN 104 and SN 106A, MN 104 transmits a 503B RRC reconfiguration message to UE 102. When UE 102 receives the 503C RRC reconfiguration message, UE 102 determines that the 504C MCG has failed. In response to the MCG failure, UE 102 suspends the transmission of the 506C MCG. Even if UE 102 enables the MCG fast recovery function, UE 102 also suspends the transmission of the 508CSCG in response to the MCG failure. Furthermore, even if UE 102 enables the MCG fast recovery function, UE 102 can also perform an RRC connection re-establishment procedure with MN 104 in response to the MCG failure. In response to performing the RRC connection re-establishment procedure, UE 102 can release the connection with SN 106A. To perform the RRC connection re-establishment procedure, UE 102 performs a random access procedure with MN 104 and transmits an RRC re-establishment request message to MN 104 during the random access procedure. Then, in response to the RRC re-establishment request message, UE 102 may receive an RRC re-establishment message from MN 104, allowing UE 102 to recover from the MCG failure based on the RRC re-establishment message. UE 102 restarts MCG transmission for SRB1 and, in response to the RRC re-establishment message, transmits an RRC re-establishment complete message to MN 104 via SRB1. To perform the RRC re-establishment procedure, UE 102 may apply certain default configurations (e.g., as specified in 3GPP TS 36.331 or 38.331) so that MN 104 can communicate with UE 102 using the default configuration after the RRC connection re-establishment procedure. After transmitting the RRC re-establishment message, MN 104 may transmit a 530C RRC reconfiguration message to UE 102. In response, UE 102 transmits a 532C RRC reconfiguration complete message to MN 104. MN 104 may include multiple configurations in the RRC reconfiguration message 530C. For example, MN 104 may include a first configuration in the RRC reconfiguration message 530C. In another example, if UE 102 has not released the first configuration due to applying the default configuration, MN 104 may indicate the release of the first configuration in the RRC reconfiguration message 530C. In yet another example, MN 104 may include a complete configuration with a complete configuration indicator in the RRC reconfiguration message 530C. Therefore, inconsistencies in configuration between UE 102 and MN 104 can be avoided. UE 102 may restart MCG transmissions for SRB2 and DRB in response to the RRC reconfiguration message 530C.

[0108] In some implementations, UE 102 can perform an RRC connection re-establishment procedure (582C) with base station 106B, which is similar to the RRC connection re-establishment procedure (582C). Then, similar to events 530C and 532C, base station 106B can transmit an RRC reconfiguration message to UE 102 after transmitting the RRC re-establishment message, and receive an RRC reconfiguration complete message from UE 102.

[0109] In some implementations, if MN 104 is a gNB, the RRC Re-establishment Request message, RRC Re-establishment message, and RRC Re-configuration Complete message can be RRCReestablishmentRequest, RRCReestablishment, and RRCReestablishmentComplete messages, respectively. In other implementations, if MN 104 is an eNB or ng-eNB, the RRC Re-establishment Request message, RRC Re-establishment message, and RRC Re-configuration Complete message can be RRCConnectionReestablishmentRequest, RRCConnectionReestablishment, and RRCConnectionReestablishmentComplete messages, respectively.

[0110] Next, refer to Figures 6A to 11 Several methods that the UE can implement to determine which SRB is used to communicate NAS messages or measurement report messages based on whether an MCG failure occurs are discussed.

[0111] First refer to Figure 6A For example, it can be Figure 1A Example method 600A for managing NAS message communication is implemented in UE 102. Method 600A begins at block 602A, where UE 102 is in DC with MN and SN (Event 302). In block 604A, UE 102 determines whether an MCG failure has occurred. If UE 102 determines that an MCG failure has occurred (Event 304), then in block 606A, UE 102 communicates NAS messages with SN via a first SRB using SCG radio resources (Event 308). On the other hand, if UE 102 determines that an MCG failure has not occurred, then in block 608A, UE 102 communicates NAS messages with MN via a second SRB using MCG radio resources. In some implementations, the first SRB is SRB3 and the second SRB is SRB2.

[0112] Figure 6BThis is a flowchart of example method 600B, which begins at block 602B, where UE 102 is in DC with MN and SN (Event 302). In block 604B, UE 102 determines whether an MCG failure has occurred. If UE 102 determines that an MCG failure has occurred (Event 304), then in block 606B, UE 102 communicates a NAS message with SN via the SCG link of the separated SRB (Event 308). On the other hand, if UE 102 determines that an MCG failure has not occurred, then in block 608B, UE 102 communicates a NAS message with MN via the MCG link of the separated SRB. In some implementations, the separated SRB is separated SRB2. In other implementations, the separated SRB is separated SRB1.

[0113] Figure 7A This is a flowchart of example method 700A, which begins at block 702A, where UE 102 is in DC with MN and SN (Event 302). In block 704A, UE 102 determines whether an MCG failure has occurred. If UE 102 determines that an MCG failure has not occurred, then in block 708A, UE 102 communicates a NAS message with MN via the second SRB using MCG radio resources. On the other hand, if UE 102 determines that an MCG failure has occurred (Event 304), then in block 710A, UE 102 determines whether the MCG fast recovery function is enabled. If UE 102 determines that the MCG fast recovery function is enabled, then in block 706A, UE 102 communicates a NAS message with SN via the first SRB using SCG radio resources (Event 308). If UE 102 determines that the MCG fast recovery function is disabled, then in block 712A, UE 102 suspends the transmission of NAS messages. In some implementations, the first SRB is SRB3 and the second SRB is SRB2.

[0114] Figure 7BThis is a flowchart of example method 800A, which begins at block 702B, where UE 102 is in DC with MN and SN (Event 302). In block 704B, UE 102 determines whether an MCG failure has occurred. If UE 102 determines that an MCG failure has not occurred, then in block 708B, UE 102 communicates a NAS message with MN via the MCG link of the separated SRB. On the other hand, if UE 102 determines that an MCG failure has occurred (Event 304), then in block 710B, UE 102 determines whether the MCG fast recovery function is enabled. If UE 102 determines that the MCG fast recovery function is enabled, then in block 706B, UE 102 communicates a NAS message with SN via the SCG link of the separated SRB (Event 308). If UE 102 determines that the MCG fast recovery function is disabled, then in block 712B, UE 102 suspends the transmission of NAS messages. In some implementations, the first SRB is SRB3, and the second SRB is SRB2.

[0115] Figure 8A This is a flowchart of example method 800A, which begins at block 802A, where UE 102 is in DC with MN and SN (Event 302). In block 804A, UE 102 determines whether an MCG failure has occurred. If UE 102 determines that an MCG failure has not occurred, then in block 808A, UE 102 communicates a NAS message with MN via SRB2 using MCG radio resources. On the other hand, if UE 102 determines that an MCG failure has occurred (Event 304), then UE 102 determines in block 806A whether SRB2 is a separate SRB. If UE 102 determines that SRB2 is a separate SRB, then in block 810A, UE 102 communicates a NAS message with SN via the SCG link of separate SRB2 (Event 308). If UE 102 determines that SRB2 is not a separate SRB, then UE 102 determines in block 812A whether SRB3 is available. If UE 102 determines that SRB3 is available, then in block 814A, UE 102 uses SCG radio resources to communicate NAS messages with SN via SRB3 (Event 308). If UE 102 determines that SRB3 is unavailable, then in block 816A, UE 102 suspends the transmission of NAS messages.

[0116] Figure 8B It is similar to Figure 8A The flowchart of example method 800B. This example method is related to... Figure 8A The similar blocks discussed below are labeled with the same number. Figure 8A and Figure 8BThe differences between scenarios are as follows: If UE 102 determines that SRB3 is unavailable, then in block 818B, UE 102 determines whether SRB1 is a separate SRB. If UE 102 determines that SRB1 is a separate SRB, then in block 820B, UE 102 communicates a NAS message with SN via the SCG link of separate SRB1 (Event 308). If UE 102 determines that SRB1 is not a separate SRB, then in block 822B, UE 102 suspends the transmission of NAS messages.

[0117] Now for reference Figure 9 For example, it can be Figure 1A Example method 900 for handling MCG transmissions is implemented in UE 102. Method 900 begins at block 902, where UE 102 is in DC with MN and SN (Event 402). In block 904, UE 102 determines that an MCG failure has occurred (Event 404). In block 906, in response to the MCG failure, UE 102 suspends MCG transmission and transmits an MCG failure information message to SN (Events 406 and 408). After transmitting the MCG failure information, in block 908, UE 102 receives an RRC reconfiguration message from SN (Event 412). In block 910, UE 102 determines whether the RRC reconfiguration message includes the mobility IE of PCell. If UE 102 determines that the RRC reconfiguration message includes the mobility IE of PCell, then in block 912, UE 102 restarts MCG transmission, and in block 914, performs random access on PCell. During or after random access, at block 916, UE 102 transmits an RRC reconfiguration complete message on the PCell via MCG transmission. After transmitting the RRC reconfiguration complete message, at block 918, UE 102 transmits communication data on the PCell via MCG transmission. Alternatively, if UE 102 determines that the RRC reconfiguration message does not include the mobility IE for the PCell, then at block 920, UE 102 maintains a pause in MCG transmission, and at block 922, transmits an RRC reconfiguration complete message to the SN via SCG transmission. In some implementations, the mobility IE may be a MobilityControlInfo IE or a ReconfigurationWithSync IE.

[0118] Next reference Figure 10A For example, it can be Figure 1AAn example method 1000A for processing the transmission of MN measurement report messages (i.e., MN's measurement report messages) is implemented in UE 102. Method 1000A begins at block 1002A, where UE 102 is in DC with MN and SN (event 402). In block 1004A, UE 102 determines whether an MCG failure has occurred. If UE 102 determines that an MCG failure has occurred (event 404), then in block 1006A, UE 102 transmits an MN measurement report message to SN via SRB3 using SCG radio resources (event 420). On the other hand, if UE 102 determines that an MCG failure has not occurred, then in block 1006A, UE 102 transmits an MN measurement report message to MN via SRB1 using MCG radio resources. Blocks 1004A, 1006A, and 1008A are in... Figure 10A They are collectively referred to as Block 1050A.

[0119] Figure 10B This is a flowchart of example method 1000B, which begins at block 1002B, where UE 102 is in DC with MN and SN (Event 402). In block 1004B, UE 102 determines whether an MCG failure has occurred. If UE 102 determines that an MCG failure has occurred (Event 404), then in block 1006B, UE 102 transmits an MN measurement report message to SN via the SCG link separated from SRB1 (Event 308). On the other hand, if UE 102 determines that an MCG failure has not occurred, then in block 1008B, UE 102 transmits an MN measurement report message to MN via the MCG link separated from SRB1. Blocks 1004B, 1006B, and 1008B... Figure 10B These are collectively referred to as Block 1050B.

[0120] Figure 11This is a flowchart of example method 1100, which begins at block 1102, where UE 102 is in DC with MN and SN (event 402). In block 1104, UE 102 in DC generates a measurement report message. In block 1006B, UE 102 determines whether the measurement report message is an MN measurement report message or an SN measurement report message (i.e., UE 102 transmits an SN measurement report message due to the measurement configuration configured by SN). In the case of an MN measurement report message, UE 102 executes either block 1050A or 1050B. In the case of an SN measurement report message, in block 1010, UE 102 determines whether an SCG failure has occurred. If UE 102 determines that an SCG failure has occurred, then in block 1112, UE 102 transmits an SN measurement report message to SN via SRB1 using MCG radio resources. On the other hand, if UE 102 determines that SCG failure has not occurred, then in block 1114, UE 102 uses MCG radio resources to transmit an SN measurement report message to MN via SRB1.

[0121] In some implementations, UE 102 can determine that the SCG link with the SN has failed. The SCG failure can be a radio link failure, an SCG configuration failure, an SRB3 integrity failure, an SCG reconfiguration synchronization failure, or a PSCell change failure.

[0122] Now for reference Figure 12 For example, it can be Figure 1A Example method 1200 for managing NAS message communication is implemented in MN 104. Method 1200 begins at block 1202, where MN 104 communicates with the UE and SN located in the DC (Event 302). In block 1204, MN 104 determines whether an MCG failure has occurred for the UE. If MN 104 determines that an MCG failure has occurred (Event 314), then in block 1206, MN 104 communicates a NAS message with the UE via the SN (Event 318). On the other hand, if MN 104 determines that an MCG failure has not occurred, then in block 1208, UE 102 communicates a NAS message with the UE using MCG radio resources.

[0123] Figure 13This is a flowchart of example method 1300, which begins at block 1302, where MN 104 communicates with the UE located in the DC and the SN (Event 302). In block 1304, MN 104 receives a NAS message for the UE located in the DC from the core network (Event 316). In block 1306, MN 104 generates a DLInformationTransfer message including the NAS message. In block 1308, MN 104 determines whether an MCG failure has occurred for the UE. If MN 104 determines that an MCG failure has occurred (Event 314), then in block 1310, MN 104 sends an RRC Transfer message including the DLInformationTransfer message to the SN. If MN 104 determines that an MCG failure has not occurred, then in block 1312, MN 104 sends a DLInformationTransfer message to the UE using MCG radio resources.

[0124] Next reference Figure 14 For example, it can be done Figure 1A Example method 1400 for configuring measurement configuration during MCG failure is implemented in MN 104. Method 1400 begins at block 1402, where MN 104 and the UE in the DC are communicating (event 402). In block 1404, MN 104 determines whether an MCG failure has occurred for the UE (event 410). After MN 104 determines that an MCG failure has occurred for the UE, in block 1406, MN 104 sends an RRC reconfiguration message including the measurement configuration to the UE via the SN (events 412, 414). In block 1408, in response to the RRC reconfiguration message, MN 104 receives an RRC reconfiguration complete message from the UE via the SN (events 416, 418).

[0125] Figure 15This is a flowchart of example method 1500, which begins at block 1502, where MN 104 communicates with the UE located in the DC (events 302, 402) and the SN. In block 1504, MN 104 receives a RAN-CN interface message from the core network indicating a fallback procedure for the UE located in the DC. In block 1506, MN 104 generates an RRC reconfiguration message (event 412) including a measurement configuration that configures the carrier frequency of the UE's target RAT. In block 1508, MN 104 determines whether an MCG failure has occurred for the UE. If MN 104 determines that an MCG failure has occurred (events 314, 410), then in block 1510, MN 104 sends an RRC transmission message including the RRC reconfiguration message to the SN. If MN 104 determines that an MCG failure has not occurred, then in block 1512, MN 104 sends an RRC reconfiguration message to the UE using the MCG radio resources.

[0126] Next reference Figure 16 For example, it can be Figure 1A Example method 1600 for processing MN RRC messages is implemented in SN 106A. Method 1600 begins at block 1602, where SN 106A communicates with MN and the UE located in DC (events 302, 402). In block 1604, SN 106A receives at least one MR RRC message: a ULInformationTransfer message, an RRC reconfiguration complete message, and a measurement report message (events 308, 416, 422). In block 1606, SN 106A generates at least one RAN interface message including at least one MN RRC message. In block 1608, SN 106A transmits at least one RAN interface message to MN 104.

[0127] Next reference Figure 17A For example, it can be Figure 1AExample method 1700A for managing the transmission of response messages is implemented in UE 102. Method 1700A begins at block 1702A, where UE 102 is in DC with MN and SN (Event 502A). Then, in block 1704A, UE 102 in DC receives a message from MN using MCG radio resources. In block 1706A, UE 102 determines whether an MCG failure has occurred. If UE 102 determines that an MCG failure has occurred (Event 504A), then in block 1708A, UE 102 responds to this message by transmitting a response message to SN using SCG radio resources (Event 516A). On the other hand, if UE 102 determines that an MCG failure has not occurred, then in block 1710A, UE 102 responds to this message by transmitting a response message to MN using MCG radio resources. Blocks 1706A, 1708A, and 1710A are... Figure 17A They are collectively referred to as Block 1750A.

[0128] In some implementations, the SN may forward the response message to the MN. In other implementations, the SN may forward the response message or its content to the core network (e.g., CN 110). In some implementations, the message may be an RRC message, and the response message may be an RRC response message. For example, the RRC message may be an RRC reconfiguration message, and the RRC response message may be an RRC reconfiguration complete message. In another example, the RRC message may be a UEInformationRequest message, and the RRC response message may be a UEInformationResponse message. In yet another example, the RRC message may be a UECapabilityEnquiry message, and the RRC response message may be a UECapabilityInformation message. In other implementations, as described above, the message may be a DL NAS message, and the response message may be a UL NAS response message.

[0129] Next reference Figure 17B For example, it can be Figure 1AExample method 1700B for managing the transmission of response messages is implemented in UE 102. Method 1700B begins at block 1702B, where UE 102 is in DC with MN and SN (Event 502A). Then, at block 1704B, UE 102 in DC receives a message from SN using SCG radio resources. At block 1706B, UE 102 determines whether an SCG failure has occurred. If UE 102 determines that an SCG failure has occurred, then at block 1708B, UE 102, in response to the message, transmits a response message to MN using MCG radio resources. On the other hand, if UE 102 determines that an SCG failure has not occurred, then at block 1710B, UE 102, in response to the message, transmits a response message to SN using SCG radio resources.

[0130] In some implementations, the SN may forward the response message to the MN. In other implementations, the SN may forward the response message or its content to the core network (e.g., CN 110). In some implementations, as described above, the message may be an RRC message, and the response message may be an RRC response message. In other implementations, as described above, the message may be a DL NAS message, and the response message may be a UL NAS response message.

[0131] Next reference Figure 17C For example, it can be Figure 1A Example method 1700C for managing the transmission of response messages is implemented in UE 102. Method 1700C begins at block 1702C, where UE 102 is in DC with MN and SN (event 502A). Then, in block 1704C, UE 102 in DC receives a message for MN or SN. In block 1706A, UE 102 determines whether the message was received from MN or SN. If the message was received from MN, then in block 1708C, UE 102 performs the following... Figure 17A As described in block 1750A. If the message is received from the SN, then in block 1710C, UE 102 determines whether an SCG failure has occurred. If UE 102 determines that an SCG failure has occurred, then in block 1712C, UE 102 ignores the message. On the other hand, if UE 102 determines that an SCG failure has not occurred, then in block 1714C, UE 102 responds to the message by transmitting a response message to the SN using SCG radio resources.

[0132] In some implementations, the SN may forward the response message to the MN. In other implementations, the SN may forward the response message or its content to the core network (e.g., CN 110). In some implementations, as described above, the message may be an RRC message, and the response message may be an RRC response message. In other implementations, as described above, the message may be a DL NAS message, and the response message may be a UL NAS response message.

[0133] Next reference Figure 18 For example, it can be Figure 1A Example method 1800 for managing the transmission of response messages is implemented in UE 102. Method 1700A begins at block 1802, where UE 102 is in DC with MN and SN (Event 502B). Then, at block 1804, UE 102 in DC receives an RRC message from MN using MCG radio resources. At block 1806, UE 102 determines whether an MCG failure has occurred. If UE 102 determines that an MCG failure has occurred (Event 504B), then at block 1808, UE 102 ignores the RRC message and transmits an MCG failure information message to SN using SCG radio resources (Events 508B, 570B). On the other hand, if UE 102 determines that an MCG failure has not occurred, then at block 1810, UE 102 responds to the RRC message by transmitting an RRC response message to MN using MCG radio resources.

[0134] In some implementations, if UE 102 receives a DL NAS message from MN using MCG radio resources before MCG failure, UE 102 ignores the DL NAS message without responding to the MCG failure. In one implementation, during an MCG failure, UE 102 may respond to the DL NAS message by transmitting a UL NAS message to SN using SCG radio resources. In another implementation, after UE 102 recovers from the MCG failure, UE 102 may use MCG radio resources to transmit a UL MAS message to MN.

[0135] Next reference Figure 19 For example, it can be Figure 1AExample method 1900 for managing ongoing RRC procedures is implemented in UE 102. Method 1900 begins at block 1902, where UE 102 is in DC with MN and SN (Event 502C). In block 1904, UE 102 determines that an MCG failure has occurred (Event 504C). UE 102 then determines whether an RRC reconfiguration procedure initiated by MN is in progress. If UE 102 determines that an RRC reconfiguration procedure initiated by MN is in progress (Event 503C), then in block 1908, in response to the MCG failure, UE 102 performs an RRC connection reconstruction procedure (Event 582C). On the other hand, if UE 102 determines that there is no ongoing RRC reconfiguration procedure initiated by MN, then in block 1910, in response to the MCG failure, UE 102 transmits an MCG failure information message to SN using SCG radio resources (Event 424A).

[0136] Next reference Figure 20 For example, it can be Figure 1A Example method 2000 for managing an ongoing RRC procedure is implemented in UE 102. Method 2000 begins at block 2002, where UE 102 is in DC with MN and SN (Event 302). At block 1904, UE 102 determines that an MCG failure has occurred (Event 304). Then, at block 2006, in response to the MCG failure, UE 102 transmits an MCG failure information message to SN using SCG radio resources. During the MCG failure, at block 2008, UE 102 determines whether there is a ULNAS message or a UE-initiated MN UL RRC message to transmit. If UE 102 determines that there is a UL NAS message or a UE-initiated MN UL RRC message to transmit, then at block 2010, UE 102 transmits a UL NAS message or a UE-initiated MN UL RRC message to MN using MCG radio resources after recovering from the MCG failure. On the other hand, if UE 102 determines that there is neither a UL NAS message nor a UE-initiated MN UL RRC message to transmit, then the method ends.

[0137] The UL NAS message is as described above. In some implementations, the MN UL RRC message is a ULRRC message transmitted by UE 102 on SRB1, rather than an RRC response message in response to a received DL RRC message generated by MN. For example, the MN ULRRC message could be a UE assistance information message. In another example, the MN UL RRC message could be a measurement report message associated with the measurement configuration configured by MN.

[0138] In some implementations, if UE 102 determines that there is an SN UL RRC message to transmit during an MCG failure, UE 102 transmits the SN UL RRC message to the SN using SCG radio resources. The SN UL RRC message is a UL RRC message transmitted by UE 102 on SRB3. For example, the SN UL RRC message may be an RRC reconfiguration complete message in response to a received RRC reconfiguration message generated by the SN. In another example, the SN UL RRC message may be a UE auxiliary information message for the SN. In yet another example, the SN UL RRC message may be a measurement report message associated with a measurement configuration configured by the SN. In yet another example, the SN UL RRC message may be a ULInformationTransferMRDC message.

[0139] The following additional considerations apply to the foregoing discussion.

[0140] User equipment (e.g., UE 102) that can implement the technologies of this disclosure can be any suitable device capable of wireless communication, such as a smartphone, tablet computer, laptop computer, mobile game console, point-of-sale (POS) terminal, health monitoring device, drone, camera, media streaming dongle or other personal media device, wearable device such as a smartwatch, wireless hotspot, femtocell base station or broadband router. Furthermore, in some cases, the user equipment can be embedded in electronic systems such as a vehicle's head unit or an advanced driver assistance system (ADAS). Additionally, the user equipment can operate as an Internet of Things (IoT) device or a mobile internet device (MID). Depending on the type, the user equipment may include one or more general-purpose processors, computer-readable storage, a user interface, one or more network interfaces, one or more sensors, etc.

[0141] Some embodiments described in this disclosure include logic or multiple components or modules. A module can be a software module (e.g., code or machine-readable instructions stored on a non-transitory machine-readable medium) or a hardware module. A hardware module is a tangible unit capable of performing a specific operation and can be configured or arranged in a particular manner. A hardware module may include permanently configured dedicated circuitry or logic (e.g., as a dedicated processor, such as a field-programmable gate array (FPGA) or application-specific integrated circuit (ASIC), digital signal processor (DSP)) to perform certain operations. A hardware module may also include programmable logic or circuitry (e.g., contained within a general-purpose processor or other programmable processor) temporarily configured by software to perform certain operations. The decision to implement a hardware module with dedicated and permanently configured circuitry or temporarily configured circuitry (e.g., configured by software) may be driven by cost and time considerations.

[0142] When implemented in software, the technology can be provided as part of an operating system, a library used by multiple applications, a specific software application, etc. This software can be executed by one or more general-purpose processors or one or more dedicated processors.

[0143] The following list reflects various embodiments explicitly contemplated by this disclosure.

[0144] Example 1. A method for uplink transmission in a UE communicating with a DC, MN, and SN, comprising: determining, by processing hardware, that a radio connection with the MN has failed; and, prior to the restoration of the radio connection with the MN, having the processing hardware communicate a NAS message with the MN via the SN using radio resources of the SN to perform a NAS procedure with the MN.

[0145] Example 2. The method according to Example 1, wherein the NAS message is a UL NAS message; and the NAS message communicates with the MN via the SN, including transmitting the UL NAS message to the SN.

[0146] Example 3. The method according to Example 1, wherein the NAS message is a DL NAS message; and the NAS message communicates with the MN via the SN, including receiving the DL NAS message from the SN.

[0147] Example 4. The method according to any one of Examples 1-3 further includes: transmitting an indication of a failed radio connection to the SN by processing hardware.

[0148] Example 5. The method as described in any of the preceding examples further includes: suspending MCG communication by processing hardware in response to determining that the radio connection with the MN has failed.

[0149] Example 6. The method as described in any of the preceding examples further includes: suspending SCG communication by processing hardware in response to determining that the radio connection with the MN has failed.

[0150] Example 7. The method as described in any of the preceding examples further includes: after determining that the radio connection with the MN has failed, receiving an RRC reconfiguration message related to the MCG from the SN.

[0151] Example 8. The method described in Example 7, wherein the RRC reconfiguration configuration configures the UE to perform at least one of (i) intra-frequency measurement, (ii) inter-frequency measurement, (iii) or inter-RAT measurement.

Claims

1. A method for uplink transmission in a user equipment (UE) communicating with a primary node (MN) and a secondary node (SN) via dual connectivity (DC), the method comprising: The UE determined that the radio connection with the MN had failed; The UE uses the SN's radio resources to transmit an indication of a failed radio connection to the SN; After confirmation and before radio connection is restored, the UE detects the uplink non-access stratum ULNAS message transmitted to the MN; as well as After the radio connection with the MN is restored, the UE uses the MN's radio resources to transmit a UL NAS message to the MN.

2. The method of claim 1, further comprising: The NAS process between the UE and the core network is performed. Among them, UL NAS messages are associated with NAS processes.

3. The method as described in claim 2, wherein, The NAS process includes performing either the Evolved Packet System (EPS) Mobility Management (EMM) process or the EPS Session Management (ESM) process.

4. The method of claim 2, wherein, The NAS process includes performing either the 5G Mobility Management (5GMM) process or the 5G Session Management (5GSM) process.

5. The method according to any one of claims 1-4, wherein, Transmitting NAS uplink messages to MN includes transmitting a ULInformationTransfer message that includes UL NAS messages.

6. The method of claim 1, further comprising: The UE receives an RRC reconfiguration message from the SN related to the failed radio connection; as well as Based on the RRC reconfiguration message, determine whether the UE should use the radio resources of the primary cell group (MCG) to restart uplink transmission.

7. The method of claim 6, further comprising: In response to the determination of the mobility of the primary cell (PCell) indicated by the RRC reconfiguration message, the uplink transmission is restarted using the radio resources of the MCG.

8. The method of claim 6, wherein, RRC reconfiguration messages include the MobilityControlInfo information element (IE) or the ReconfigurationWithSync IE.

9. The method according to any one of claims 1 to 4, further comprising: The MCG fast recovery process is performed by the processing hardware, including: Transmit an MCGFailureInformation message as an indication of the dialed radio connection; and The request for RRC reconfiguration is received from the MN via a separate radio bearer branch associated with the SN.

10. The method as claimed in any one of claims 1 to 4, wherein, Determining that a radio connection has failed includes: Detect radio link failure (RLF) on the MCG link; or The system detected a failure in the reconfiguration process related to the MCG link.

11. A UE, including processing hardware, and configured to implement the method according to any one of the preceding claims.

12. A method for performing downlink transmission in a first base station operating as a primary node (MN) to provide dual connectivity DC to a UE together with a second base station operating as a secondary node (SN), the method comprising: The MN receives downlink (DL) NAS messages addressed to the UE from the core network; The radio connection between the MN and the UE has failed, as detected by the MN. The MN prevents the MN from transmitting DL NAS messages to the UE until the radio connection has been restored; and In response to the detection that the radio connection has been restored, a DL NAS message is transmitted to the UE using the radio resources of the MN.

13. The method of claim 12, further comprising: The MN transmits an RRC reconfiguration message to the SN related to the failed radio connection.

14. The method of claim 13, further comprising: The RRC reconfiguration message includes the UE's measurement configuration.

15. The method of any one of claims 12-14, further comprising: Receive measurement reports from the UE via the SN and related to the primary cell group (MCG) associated with the MN; as well as In response to the measurement report, the MN initiates a recovery process to restore the radio connection with the UE.

16. The method of claim 15, wherein: The failed radio connection was associated with the first cell of the MCG, and The restored radio connection is associated with the second cell of the MCG.

17. The method of claim 12, wherein: The prevention and transmission of DL NAS using MN's radio resources in the first case occurs; In the second case, the method further includes: Determine to direct the UE to different base stations. Discard DL NAS messages, and The MN transmits an indication to the core network that it did not deliver a DL NAS message to the UE.

18. A base station including processing hardware and configured to implement the method as claimed in any one of claims 12-17.

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