Systems and methods for managing radio bearer compatibility in a communication network

Abstract

A user equipment (UE) for managing radio bearers communicates with a first base station via a first radio bearer associated with a dedicated control channel and configured to carry at least application layer measurement report information, the radio bearer being associated with a logical channel identifier (2502); receives a message related to (i) the first radio bearer or (ii) a second radio bearer having a logical channel identifier and terminating at the second base station, from a radio access network (RAN) including the first base station and the second base station (2504); and releases or reconfigures the first radio bearer in response to the message (2506).

Description

Technical Field

[0001] The present disclosure relates to a wireless communication system, and more particularly, to a wireless communication system for managing radio bearer compatibility when a user equipment (UE) establishes or re - establishes a radio connection with a base station. Background Art

[0002] The background description provided in the present disclosure is for the purpose of generally presenting the background of the present disclosure. Within the scope described in this background section, the work of the named inventors, as well as aspects that may not conform to the description of the prior art at the time of application, are neither expressly nor impliedly admitted to be the prior art for the present disclosure.

[0003] In a wireless communication system, a base station supporting a certain radio access technology (RAT) communicates with a user equipment (UE) using a protocol for controlling radio resources corresponding to the RAT, etc. The protocol for controlling radio resources can be, for example, the radio resource control (RRC) protocol used in 4G, 5G, 6G, or a newer generation of wireless communication systems. When establishing a radio connection via the base station, the UE operates in the connection state of the protocol for controlling radio resources, which can be RAT - specific (e.g., EUTRA - RRC CONNECTED, NR - RRC CONNECTED).

[0004] The UE and the base station can use signaling radio bearers (SRBs) to exchange RRC messages as well as non - access stratum (NAS) messages. There are several types of SRBs: SRB1 resources carry RRC messages through a dedicated control channel (DCCH) and, in some cases, also carry NAS messages; SRB2 resources support RRC messages including recorded measurement information or NAS messages, also through the DCCH but with a lower priority than SRB1 resources; SRB3 resources support RRC messages related to measurement configuration and reporting, e.g., when the UE operates in dual - connection (DC), the measurement configuration and reporting of the secondary cell group (SCG); and SRB4 resources support RRC messages including application - layer measurement report information, also through the DCCH.

[0005] In addition, the UE and the base station use data radio bearers to transmit data on the user plane.

[0006] There are several scenarios in which a (first) base station and / or a UE determine that the UE should establish a radio connection with another (second) base station. For example, the first base station may determine to hand over the UE to the second base station and initiate a handover procedure. In another scenario, the UE may detect a radio link failure (RLF) on the radio connection with the first base station and subsequently select the second base station to re-establish the radio connection. In yet another scenario, the first base station may detect below-threshold activity of the UE over a period of time via the established connection and instruct the UE to transition to an inactive state of the RAT protocol (e.g., EUTRA-RRC INACTIVE, NR-RRC INACTIVE). At a later time, such as when the UE has moved to a different coverage area and has payload data to send to the wireless communication system, the UE operating in the inactive state selects or reselects the second base station and then transitions back to the connected state.

[0007] In some of these scenarios, the UE and the first base station use SRB4 which may not be supported by the second base station. The second base station generally does not know the non-supported configuration of the SRB. Therefore, the second base station may provide a configuration that conflicts with the SRB4 configuration to the UE, or the UE may continue to use SRB4 to send information that the second base station does not process.

[0008] As a more specific example, the SRB or DRB has different logical channel identifiers. For example, SRB4 may have a logical channel identifier value of "4". When the second base station supports SRB4, the second base station knows the logical channel identifier value of SRB4 assigned by the first base station to the UE. Therefore, when the second base station configures a new radio bearer for the UE, the second base station does not use the logical channel identifier value that has been assigned to SRB4. However, when the second base station does not support the SRB4 configuration, the second base station is not aware of the existence of the SRB4 configuration and its logical channel identifier value. As a result, the second base station may associate a DRB with the same logical channel identifier value as that assigned by the first base station to SRB4. This conflict in the logical channel identifier assignment can lead to communication failures between the UE and the second base station.

[0009] In addition, when the second base station supports SRB4, the second base station can apply a full configuration to the radio connection between the UE and the second base station in some cases. For example, when the second base station cannot identify at least one configuration of the connection, or when the second base station attempts to save processing resources by not filtering the (multiple) configurations associated with the connection between the UE and the first base station, the second base station can provide a full configuration. As another example, the second base station can be manufactured or operated by an entity different from the first base station. The 3rd Generation Partnership Project (3GPP) specifications, particularly 3GPP TS 36.331 v15.7.0, do not address the scenario where the second base station provides a full configuration involving SRB4 to the UE. As a result, different UEs can handle the full configuration differently, and the second base station and the UE cannot communicate correctly. SUMMARY OF THE INVENTION

[0010] In a radio access network (RAN) of the present disclosure, a first base station (e.g., an evolved Node B (eNB)) configures a UE with SRB4, and the UE subsequently establishes or re-establishes a radio connection with a second base station (e.g., another eNB) as part of a handover procedure, a connection re-establishment procedure, a connection recovery procedure, etc. In some implementations, the second base station causes the UE to release SRB4 and establish another type of radio bearer to communicate with the second base station. In other implementations, the second base station causes the UE to reconfigure SRB4 for communication with the second base station.

[0011] In various implementations, the second base station causes the UE to release SRB4 by including a configuration for a DRB, omitting the configuration of SRB4, including an explicit indicator indicating that the UE releases SRB4, omitting an explicit indicator indicating that the UE retains SRB4, providing a full configuration omitting the SRB4 configuration, etc. The second base station can use one of these techniques when formatting a handover command, an RRC reconfiguration command, an RRC recovery command, etc. Since the second base station communicates with the UE via the first base station in at least some of these scenarios, in some implementations, the first base station modifies the message addressed to the UE by the second base station. By causing the UE to release SRB4 before applying the DRB configuration, the second base station prevents the UE from using the same logical channel identifier with two different radio bearers.

[0012] In another implementation, the UE reconfigures SRB4 according to a message from the second base station. The term "reconfiguration" as used herein may refer to the UE (i) reconfiguring an existing SRB4 to generate a new SRB4 configuration for the second base station, or (ii) releasing the existing SRB4 and generating a new SRB4 according to a new configuration provided by the second base station. That is, if the second base station supports SRB4, the second base station may send a message including the new SRB4 configuration to cause the UE to replace the SRB4 configuration previously provided by the first base station with the new SRB4 configuration. If the second base station does not support SRB4, the second base station may send a message including the configuration for the DRB to the UE, such that the UE releases SRB4 before applying the DRB configuration.

[0013] Generally, the techniques disclosed in this disclosure are applied to a wireless communication system having one or more radio access networks supporting the same or different types of radio access technologies, e.g., via an unlicensed portion of the radio spectrum, such as fourth generation mobile or cellular data technology ("4G"), 4G according to the Long-Term Evolution standard ("4G-LTE"), fifth generation mobile or cellular data technology (referred to as "5G"), 5G New Radio ("NR" or "NR-U"), 5G evolved universal terrestrial radio access ("EUTRA" or "E-UTRA"), sixth generation mobile or cellular data technology ("6G"), etc. Various different types of radio access technologies may be connected to any suitable type of core network ("CN"), such as an evolved packet core network ("EPC"), a core network of the generation after EPC (such as 5GC), a core network of the generation later than 5GC, etc.

[0014] An example embodiment of these techniques is a method in a UE for managing radio bearers. The method includes communicating with a first base station via a first radio bearer associated with a dedicated control channel and configured to carry at least application layer measurement report information, the radio bearer being associated with a logical channel identifier. The method further includes receiving, from a radio access network (RAN) including the first base station and a second base station, a message related to (i) the first radio bearer or (ii) a second radio bearer having a logical channel identifier and terminating at the second base station. The method further includes releasing or reconfiguring the first radio bearer in response to the message.

[0015] Another example embodiment of these techniques is a UE having processing hardware configured to implement the above method.

[0016] Example embodiments of these techniques are a method in a radio access network (RAN) that includes a first base station supporting a first type of radio bearer and a second base station not supporting the first type of radio bearer. The method includes determining that a UE configured with a first radio bearer of the first type will obtain a radio connection to the second base station, where the radio bearer terminates at the first base station. The method further includes sending a message to cause the UE to release the first radio bearer and establish a second radio bearer of a second type, where the second radio bearer terminates at the second base station.

[0017] Another example embodiment of these techniques is a base station having processing hardware configured to implement the above method.

[0018] Another example embodiment of these techniques is a RAN including a first base station and a second base station having processing hardware configured to implement the above method. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 An example wireless communication system is depicted in accordance with at least some of the principles and techniques disclosed in the present disclosure, where a UE configured with SRB4 communicates with a RAN that manages SRB4 when the UE establishes, resumes, or re-establishes a radio connection to a base station.

[0020] Figure 2A An example message flow diagram of a handover scenario in accordance with the techniques of the present disclosure is shown, where a base station determines that a configuration for a DRB is included in a message associated with a handover procedure to release SRB4 before the handover scenario is completed.

[0021] Figure 2B An example message flow diagram of a handover scenario in accordance with the techniques of the present disclosure is shown, where a base station determines that a configuration for a DRB is included in a message associated with a handover procedure to release SRB4 after the handover scenario is completed.

[0022] Figure 3 An example message flow diagram of a handover scenario in accordance with the techniques of the present disclosure is shown, where a base station determines that a message associated with a handover procedure includes a fully configured and either omits or includes an SRB4 configuration to release or reconfigure SRB4.

[0023] Figure 4 An example message flow diagram of a handover scenario in accordance with the techniques of the present disclosure is shown, where a base station determines that an SRB4 configuration is omitted from a message associated with a handover procedure to release SRB4.

[0024] Figure 5Shows an example message flow diagram of a handover scenario according to the technology of the present disclosure, in which the base station determines whether to include or omit an explicit indicator in a message associated with the handover procedure to release or reconfigure SRB4.

[0025] Figure 6 Shows an example message flow diagram of a handover scenario according to the technology of the present disclosure, in which the UE automatically releases SRB4 in view of the handover procedure.

[0026] Figure 7A Shows an example message flow diagram of a handover scenario according to the technology of the present disclosure, in which when the SRB4 release condition and the handover condition are satisfied, the base station determines to include an explicit indicator in a message associated with the handover procedure to release SRB4.

[0027] Figure 7B Shows an example message flow diagram of a handover scenario according to the technology of the present disclosure, in which when the SRB4 release condition is satisfied before the handover condition, the base station determines to include an explicit indicator in a message associated with the handover procedure to release SRB4.

[0028] Figure 8 Shows an example message flow diagram of a handover scenario according to the technology of the present disclosure, in which when broadcasting system information to release or reconfigure SRB4, the base station determines whether to omit or include an explicit indicator.

[0029] Figure 9 Shows an example message flow diagram of a reconstruction scenario according to the technology of the present disclosure, in which the base station determines to include a configuration for DRB in a message associated with the procedure for reconstructing a radio connection to release SRB4.

[0030] Figure 10 Shows an example message flow diagram of a reconstruction scenario according to the technology of the present disclosure, in which the base station determines to include a fully configured and omit or include an SRB4 configuration in a message associated with the procedure for reconstructing a radio connection to release or reconfigure SRB4.

[0031] Figure 11 Shows an example message flow diagram of a reconstruction scenario according to the technology of the present disclosure, in which the base station determines to omit or include an SRB4 configuration in a message associated with the procedure for reconstructing a radio connection to release or reconfigure SRB4.

[0032] Figure 12 Shows an example message flow diagram of a reconstruction scenario according to the technology of the present disclosure, in which the base station determines to include or omit an explicit indicator in a message associated with the procedure for reconstructing a radio connection to release or reconfigure SRB4.

[0033] Figure 13 FIG. 2 shows an example message flow diagram of a reconstruction scenario according to the technology of the present disclosure, in which the UE automatically releases SRB4 in view of the RRC connection re - establishment procedure.

[0034] Figure 14 FIG. 6 shows an example message flow diagram of a reselection scenario according to the technology of the present disclosure, in which the base station determines that the configuration for the DRB is included in the message associated with the procedure for resuming the previously suspended radio connection to release SRB4.

[0035] Figure 15 FIG. 10 shows an example message flow diagram of a reselection scenario according to the technology of the present disclosure, in which the base station determines that the message associated with the procedure for resuming the previously suspended radio connection includes a fully configured and either omits or includes the SRB4 configuration to release or re - configure SRB4.

[0036] Figure 16 FIG. 14 shows an example message flow diagram of a reselection scenario according to the technology of the present disclosure, in which the base station determines that the message associated with the procedure for resuming the previously suspended radio connection either omits or includes the SRB4 configuration to release or re - configure SRB4.

[0037] Figure 17 FIG. 18 shows an example message flow diagram of a reselection scenario according to the technology of the present disclosure, in which the base station determines that the message associated with the procedure for resuming the previously suspended radio connection includes or omits an explicit indicator to release or re - configure SRB4.

[0038] Figure 18 FIG. 22 shows an example message flow diagram of a reselection scenario according to the technology of the present disclosure, in which the UE automatically releases SRB4 in view of the RRC connection resume procedure.

[0039] Figure 19A FIG. 26 shows an example message flow diagram of a reselection scenario according to the technology of the present disclosure, in which when the SRB4 release condition and the inactivity condition are met, the base station determines that an explicit indicator is included in the message associated with the procedure for resuming the previously suspended radio connection to release SRB4.

[0040] Figure 19B FIG. 30 shows an example message flow diagram of a reselection scenario according to the technology of the present disclosure, in which when the SRB4 release condition is met before the inactivity condition, the base station determines that an explicit indicator is included in the message associated with the procedure for resuming the previously suspended radio connection to release SRB4.

[0041] Figure 19CShows an example message flow diagram of a reselection scenario according to the technology of the present disclosure, in which, when the SRB4 release condition and the inactivity condition are met, the base station determines to include an explicit indicator in another message associated with the procedure for resuming a previously suspended radio connection to release SRB4.

[0042] Figure 20 Is a flowchart of an example method in a base station according to the technology of the present disclosure for causing a UE to release or reconfigure SRB4 in view of including and / or excluding a specific type of configuration.

[0043] Figure 21 Is a flowchart of an example method in a UE or a base station according to the technology of the present disclosure for automatically releasing SRB4 in view of the type of procedure.

[0044] Figure 22 Is a flowchart of an example method in a UE or a base station according to the technology of the present disclosure for releasing or reconfiguring SRB4 in view of including and / or excluding a specific type of indication in system information.

[0045] Figure 23 Is a flowchart of an example method in a base station according to the technology of the present disclosure for releasing SRB4 in view of detecting the SRB4 release condition.

[0046] Figure 24 Is a flowchart of an example method for managing radio bearers, which can be implemented in Figure 1 the base station 106; and

[0047] Figure 25 Is a flowchart of an example method for managing radio bearers, which can be implemented in Figure 1 the UE 102. Detailed Description

[0048] The technologies described in the present disclosure are applied to a certain type of radio bearer, SRB4, when a UE establishes or re - establishes a radio connection with a base station. However, these technologies can also be applied to other radio bearers supported by some but not all base stations operating in the RAN.

[0049] As Figure 1As shown, system 100 includes a first base station 104 and a second base station 106 of RAN 108, each of which supports the same or different RATs. For example, base station 104 may support NR, and base station 106 may support EUTRA, and vice versa. Generally, a base station that supports the NR RAT operates as a gNodeB (gNB), and a base station that supports the E-UTRA RAT and is connected to the 5GC core network (E-UTRA / 5GC) operates as a next-generation evolved Node B (ng-eNB). A base station that supports the E-UTRA RAT and is connected to the EPC core network (E-UTRA / EPC) operates as an evolved NodeB (eNB), and a base station that supports both E-UTRA / EPC and E-UTRA / 5GC operates as an ng-eNB and an eNB. Each base station 104, 106 may be communicatively connected to the same CN (e.g., EPC or 5GC) or different core networks (EPC and 5Gc). Base station 104 supports cell 124, and base station 106 supports cell 126. As Figure 1 shown, cell 124 and cell 126 may partially overlap.

[0050] Instead of NR and / or EUTRA, or in addition to NR and / or EUTRA, each base station 104, 106 may support other types of radio access technologies. Although Figure 1 two base stations 104, 106 connected to a single CN 110 are shown, system 100 may be configured with any number of base stations supporting any number of RANs, each RAN being separately connected to any number of CNs.

[0051] Base station 104 and UE 102 establish a connection, via which a data payload is sent between UE 102 and base station 104, for example, wirelessly. When establishing a connection via base station 104, UE 102 is in a connection state of the RAT protocol for controlling radio resources (e.g., EUTRA-RRC_CONNECTED, NR-RRC CONNECTED). Base station 104 maintains the context of UE 102, where the context of UE 102 includes configurations and other information associated with the connection of UE 102 to base station 104. For example, the context of UE 102 may be included in or implemented as the AS. The context of UE 102 may include the configurations of SRB1, SRB2, SRB4, DRB and / or other configurations (e.g., security configurations) associated with the connection between UE 102 and base station 104.

[0052] At some time points, the UE 102 establishes, resumes, or re - establishes a radio connection with the base station 106 for services. This can occur in various scenarios. In one scenario ("handover scenario"), the base station 104 can determine that the UE 102 is to hand over to the base station 106. In another scenario ("re - establishment scenario"), the UE 102 can detect a radio link failure (RLF) on the connection established with the base station 104, or detect an integrity check failure on SRB1, SRB2, or SRB4, and subsequently select the base station 106 for services. In yet another scenario ("re - selection scenario"), the base station 104 can detect that there has been below - threshold or no data activity for the UE 102 during some time intervals on the established connection. Once detected, the base station 104 instructs the UE 102 to enter an inactive state of the RAT protocol (e.g., EUTRA - RRC INACTIVE, NR - RRC INACTIVE). At some later time points, such as when the UE 102 has moved to a different coverage area and has payload data to send to the system, the UE 102 (which is in the inactive state) selects or re - selects the base station 106 for services.

[0053] In each of the above - mentioned scenarios, a new connection is established between the UE 102 and the base station 106, which causes the base station 106 to create a context or a second instance of the AS for the UE 102 and populate the context / second instance of the AS with configuration information associated with the connection between the UE 102 and the base station 106. In some cases, the base station 106 may not support or recognize at least one configuration associated with the connection between the UE 102 and the base station 104 (e.g., SRB4 configuration), and thus, the base station 106 generally does not know about such non - supported or unrecognizable configurations. In some cases, the base station 106 can support or recognize the configuration associated with the connection between the UE 102 and the base station 104, but provides its own configuration (e.g., full configuration, incremental configuration) to the UE 102, and the base station 106 stores the information collected during these procedures and the locally - accessible second instance of the context / AS.

[0054] In each of the above - mentioned scenarios, the base station 106 is configured to include or omit an indication for releasing or re - configuring the SRB4 configuration from the context of the UE 102 maintained by the base station 104 in a message. For example, in the handover scenario, re - establishment scenario, or re - selection scenario, the base station 106 is configured to include or omit an indication for releasing or re - configuring the SRB4 configuration in the handover command message, RRC re - configuration message, or RRC resume message, respectively.

[0055] UE 102 is equipped with processing hardware 120, 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 a dedicated processing unit. The processing hardware 120 in an example implementation includes an RRC controller 122, which is configured to receive messages from base stations 104, 106 during a handover scenario, a reconstruction scenario, or a reselection scenario according to one or more of the methods, principles, and techniques disclosed in the present disclosure, and in response to the message, release or reconfigure an existing SRB4 125 (i.e., maintained by base station 104) stored in the non-transitory computer-readable memory.

[0056] Base station 104 is equipped with processing hardware 130, 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 a dedicated processing unit. The processing hardware 130 in an example implementation includes an RRC controller 132, which is configured to initiate a handover scenario or a reselection scenario according to one or more of the methods, principles, and techniques disclosed in the present disclosure.

[0057] Base station 106 is equipped with processing hardware 140, 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 a dedicated processing unit. The processing hardware 140 in an example implementation includes an RRC controller 142, which is configured to complete a handover scenario, a reconstruction scenario, or a reselection scenario according to one or more of the methods, principles, and techniques disclosed in the present disclosure.

[0058] Although not shown, the processing hardware 120, 130, 140 may include a UE and base station interface through which the processing hardware 120, 130, 140 can communicate with each other.

[0059] Figures 2A - 2B and Figures 3 - 8 An example message flow diagram of a handover scenario between UE 102 and base stations 104, 106 in a wireless communication system 100 is generally shown.

[0060] Now turning to Figure 2A, at the start of scenario 200, the RRC controller 122 of UE 102 and the RRC controller 132 of base station 104 execute a measurement procedure 211 to establish a manner in which UE 102 performs measurements and provides measurement results to base station 104 in a report. To start executing the measurement procedure 211, UE 102 operates 202 in a connected state with base station 104 (e.g., EUTRA-RRC_CONNECTED, NR-RRC CONNECTED). When base station 104 determines 204 to request UE 102 to perform measurements (e.g., application layer measurement report (e.g., qoe-MeasReport), MDT measurement report, SON measurement report, RLF measurement report, RACH measurement report, connection establishment failure report, and / or mobility history report) and provide a corresponding report to base station 104 via a specific SRB4, base station 104 sends 206 an RRC reconfiguration message to UE 102. In some embodiments, the RRC reconfiguration message includes an SRB4 configuration associated with a specific logical channel identification value (e.g., "4"), and a measurement configuration (e.g., application layer measurement configuration, MDT measurement configuration, or / and SON measurement configuration). In other embodiments, base station 104 may include the measurement configuration in a second RRC reconfiguration message and send 207 this measurement configuration.

[0061] In response, UE 102 applies 208 the SRB4 configuration and the measurement configuration, and continues to perform measurements and generate reports. To send the requested report, UE 102 includes the report in an RRC message (e.g., MeasReportAppLayer message, UEInformationResponse message, UEAssistanceInformation message, or a newly defined RRC message) and sends 210 this RRC message to base station 104 via the configured SRB4 (associated with the logical channel identification value 4), thereby completing the measurement procedure 211. In one embodiment, the newly defined RRC message may contain segments of the RRC message.

[0062] After some time, base station 104 determines 212 to hand over UE 102 to base station 106. Accordingly, base station 104 sends 214 a handover request message to base station 106. In response, base station 106 determines 216 to configure UE 102 with a DRB configuration associated with the same logical channel identity value as the configured SRB4, either because base station 106 does not support or otherwise does not know the configured SRB, or because base station 106 supports the configured SRB4 but intends to release the configured SRB4 (i.e., the logical channel identity value assigned to the configured SRB4 can be assigned by base station 106). Base station 106 includes the configuration for the DRB in the handover command message and then sends 218 a handover request confirmation message including the handover command message (e.g., an RRCConnectionReconfiguration message, an RRCReconfiguration message) to base station 104. Subsequently, base station 104 sends 220 the handover command message to UE 102.

[0063] The handover command message causes UE 102 to release 222 SRB4 and apply 224 the DRB configuration indicated in the handover command message. Accordingly, advantageously, UE 102 verifies the handover command message because the logical channel identity value associated with the DRB configuration is only associated with the DRB configuration and not with the SRB4 configuration. In some embodiments, UE 102 may also release the measurement configuration provided by base station 104 at event 206 or 207.

[0064] Next, the UE 102 sends a handover complete message (e.g., an RRCConnectionReconfigurationComplete message, an RRCReconfigurationComplete message) to the base station 106, thereby successfully completing the handover scenario. Thus, the UE 102 operates 228 in a connected state with the base station 106, and thus the UE 102 and the base station 106 can exchange 230 data via the logical channel identifiers mapped to the DRB. For example, the UE 102 can send packets (e.g., Internet Protocol (IP) packets) via the DRB. The UE 102 can send a measurement report or other suitable report in a Packet Data Convergence Protocol (PDCP) protocol data unit (PDU) to the base station 106 via the DRB (i.e., instead of the previously configured SRB4 due to the release of the SRB4 configuration). In particular, the UE 102 can generate a PDCP SDU including the report according to the DRB configuration, encrypt the PDCP SDU, and construct a PDCP PDU including the encrypted PDCP SDU. The UE 102 sends the PDCP PDU associated with the DRB to the base station 106. In response, the base station 106 successfully processes the PDCP PDU according to the DRB configuration. Similarly, the UE 102 can receive a PDCP PDU associated with the DRB from the base station 106 and successfully process the PDCP PDU according to the DRB configuration (i.e., instead of the SRB4 configuration due to the release of the SRB4 configuration).

[0065] Now turning to Figure 2B , at the start of scenario 200, the UE 102 and the base station 104 perform 211 a measurement procedure. After a period of time, the base station 104 determines 212 to hand over the UE 102 to the base station 106. Thus, the base station 104 sends a handover request message 214 to the base station 106. In response, the base station 106 determines to configure the UE 102 with a configuration (e.g., a security configuration opposite to the DRB configuration shown in Figure 2A ), includes the configuration in a handover command message (e.g., an RRCConnectionReconfiguration message, an RRCReconfiguration message), and subsequently sends a handover request confirmation message 217 including the handover command message to the base station 104. Next, the base station 104 sends a handover command message 219 to the UE 102.

[0066] The handover command message causes the UE 102 to apply 225 the configuration included in the handover command message.

[0067] Next, UE 102 sends a handover complete message (e.g., RRCConnectionReconfigurationComplete message, RRCReconfigurationComplete message) to base station 106, thus successfully completing the handover scenario. Accordingly, UE 102 operates 227 in a connected state with base station 106.

[0068] Contrary to Figure 2A the base station 106 shown, Figure 2B the base station 106 shown in starts a reconfiguration procedure 235 by determining 216 to configure UE 102 with a DRB configuration associated with the same logical channel identity value as the configured SRB4 after the handover scenario has been successfully completed, either because the base station 106 does not support or otherwise does not know the configured SRB, or because the base station 106 supports the configured SRB4 but intends to release the configured SRB4 (i.e., thus the logical channel identity value assigned to the configured SRB4 may be assigned by the base station 106). The base station 106 includes the DRB configuration in an RRC reconfiguration message and subsequently sends 232 the RRC reconfiguration message to UE 102.

[0069] The RRC reconfiguration message causes UE 102 to release 222 SRB4 and apply 224 the DRB configuration included in the RRC reconfiguration message. Accordingly, advantageously, UE 102 verifies the RRC reconfiguration message because the logical channel identity value associated with the DRB configuration is only associated with the DRB configuration and not with the SRB4 configuration. In some embodiments, UE 102 may also release the measurement configuration provided by base station 104 at event 211.

[0070] Next, UE 102 sends a 234 RRC connection reconfiguration complete message (e.g., RRCConnectionReconfiguration message or RRCReconfiguration message) to base station 106. Accordingly, as described above in Figure 2A , UE 102 operates 228 in a connected state with base station 106, and thus UE 102 and base station 106 can exchange 230 data via the logical channel identity mapped to the DRB, thereby completing the reconfiguration procedure 235.

[0071] Now turning to Figure 3 , at the start of scenario 300, UE 102 and base station 104 perform a measurement procedure 311, similar to event 211 discussed above. Similarly to events 212, 214 discussed above, base station 104 determines 312 to hand over UE 102 to base station 106 and subsequently sends a 314 handover request message to base station 106.

[0072] In some embodiments, in response to a handover request message, the base station 106 determines 316 to configure the UE 102 with a full configuration or an incremental configuration, which may include DRB configuration (similar to event 216), and omits the SRB4 configuration. For example, when the base station 106 does not recognize at least one configuration associated with the connection between the UE 102 and the base station 104 (e.g., the SRB4 configuration), or when the base station 106 determines to save processing resources by not filtering the (multiple) configurations associated with the connection between the UE 102 and the base station 104, the base station 106 may determine to provide a full configuration or an incremental configuration. As another example, the base station 106 may simply be operated by a vendor different from the base station 104.

[0073] The base station 106 includes the full configuration or the incremental configuration in the handover command message and omits the SRB4 configuration therein, and then sends 318 a handover request confirmation message including the handover command message to the base station 104, and the base station 104 in turn sends 320 the handover command message to the UE 102, similar to event 218 and event 220.

[0074] Similar to events 222 and 224, the handover command message causes the UE 102 to release 322 the SRB4 and apply 324 the DRB configuration indicated in the handover command message. Thus, advantageously, the UE 102 verifies the handover command message because the logical channel identification value associated with the DRB configuration is only associated with the DRB configuration and not with the SRB4 configuration. In some embodiments, the UE 102 may also release the measurement configuration provided by the base station 104 at event 311.

[0075] In other embodiments, in response to a handover request message, the base station 106 determines 317 to include a full configuration or an incremental configuration in the handover command message and include the SRB4 configuration, and then sends 319 a handover request confirmation message including the handover command message to the base station 104, and the base station 104 in turn sends 321 the handover command message to the UE 102, similar to event 218 and event 220. However, contrary to events 322 and 324, the handover command message causes the UE 102 to reconfigure 323 the SRB4 in view of the SRB4 configuration indicated in the handover command message. It should be noted that the UE 102 may reconfigure the existing SRB4 maintained by the base station 104 to the new SRB4 configuration provided by the base station 106, or release the existing SRB4 and apply the new SRB4 configuration provided by the base station 106, and optionally keep the previous SRB4 configuration as it is in addition to the new SRB4 configuration. Thus, advantageously, since both the UE 102 and the base station 106 are configured to communicate via the new SRB4, the UE 102 is able to communicate with the base station 106 via the new SRB.

[0076] In response to the application of 324 DRB configuration or reconfiguration of 323 SRB, UE 102 sends a 326 handover complete message to base station 106, similar to event 226. Thus, UE 102 operates 328 in a connected state with base station 106 via the DRB or the new SRB, and thus UE 102 and base station 106 can communicate via the DRB or the new SRB.

[0077] Now turning to Figure 4 , at the start of scenario 400, UE 102 and base station 104 perform a 411 measurement procedure, similar to event 211 discussed above. Similar to event 212 discussed above, base station 104 determines 412 to hand over UE 102 to base station 106. Base station 104 includes the SRB4 configuration in the handover request message and then sends a 414 handover request message to base station 106, similar to event 214.

[0078] In response to the handover request message, base station 106, which does not support SRB4 in scenario 400, determines 416 to omit the SRB4 configuration and include a DRB configuration for UE 102. Base station 106 omits the SRB4 configuration in the handover command message and includes the configuration for the DRB, and then sends a 418 handover request confirmation message including the handover command message to base station 104, similar to event 218. Subsequently, base station 104 sends a 420 handover command message to UE 102, similar to event 220.

[0079] In response, UE 102 and base station 106 proceed to events 422, 424, 426, 428, and 430, similar to events 222, 224, 226, 228, and 230.

[0080] Now turning to Figure 5 , at the start of scenario 500, UE 102 and base station 104 perform a 511 measurement procedure, similar to event 211 discussed above. Also similar to events 212 and 214 discussed above, base station 104 determines 512 to hand over UE 102 to base station 106 and then sends a 514 handover request message to base station 106.

[0081] In some embodiments, in response to a handover request message, base station 106 determines to provide an SRB4 release indication or omit an SRB4 retention indication for UE 102 at 516. Base station 106 includes the SRB4 release indication and omits the SRB4 retention indication in a dedicated field of the handover command message, and then sends a handover request confirmation message including the handover command message to base station 104 at 518, and base station 104 in turn sends a handover command message to UE 102 at 520, similar to events 218 and 220. In response, UE 102 and base station 106 proceed to events 522, 524, 526, 528, and 530, similar to events 222, 224, 226, 328, and 330.

[0082] Although not shown, base station 104 instead of base station 106 may determine to provide an SRB4 release indication or omit an SRB4 retention indication for UE 102. Accordingly, base station 104 includes the SRB4 release indication in the handover command message and omits the SRB4 retention indication, and then sends the handover command message to UE 102. Thus, since base station 106 communicates with UE 102 via base station 104, base station 104 modifies the handover command message sent by base station 106 to UE 102.

[0083] In other embodiments, in response to a handover request message, base station 106 determines to omit the SRB4 release indication and include the SRB4 retention indication in the handover command message at 517, and then sends a handover request confirmation message including the handover command message to base station 104 at 519, and base station 104 in turn sends a handover command message to UE 102 at 521, similar to events 218 and 220. In response, UE 102 and base station 106 proceed to events 523, 526, 528, and 530, similar to events 323, 226, 328, and 330.

[0084] Now turning to Figure 6 , at the start of scenario 600, UE 102 and base stations 104, 106 proceed to events 611, 612, 614, 617, and 619, similar to events 211, 212, 214, 218, and 220. In response to receiving the handover command message at 619, UE 102 proceeds to events 622, 624, 626, and 628, similar to events 222, 224, 226, and 228. Accordingly, UE 102 automatically releases SRB4 in response to the handover command message or after the handover scenario is completed. For example, in embodiments where the RATs of base station 104 and base station 106 are different, UE 102 automatically releases SRB4 due to an inter-RAT handover from base station 104 to base station 106.

[0085] Now turning to Figure 7A, at the start of scenario 700, UE 102 and base station 104 execute a 711 measurement procedure, similar to event 211. After a period of time, base station 104 can determine 713 to not only hand over UE 102 to base station 106 but also release SRB4. In other words, if the SRB4 release condition is the same as the handover condition, base station 104 can determine to hand over UE 102 to base station 106 and release SRB4. For example, when base station 104 receives an indication that the measurement results of cell 124 or cell 126 at UE 102 meet a certain threshold (e.g., a fixed threshold, an offset value), base station 104 determines that the measurement results meet the handover condition and the SRB4 release condition, and then sends a 737 RRC reconfiguration message (e.g., RRCConnectionReconfiguration message or RRCReconfiguration message) to UE 102 to cause UE 102 to release 722 SRB4. Base station 104 can include a dedicated field (e.g., SRB4 release indicator, srb-ToReleaseListExt-r15 or SRB4 configuration) in the RRC reconfiguration message to cause UE102 to release SRB4. Subsequently, base station 104 sends a 714 handover request message to base station 106.

[0086] In one implementation, the measurement results indicate that the signal strength or quality of cell 126 meets the threshold. For example, the measurement results can include an event identifier indicating the event. The event can be event A3 (indicating that the neighboring cell becomes better than the serving cell (e.g., the primary cell (PCell), the primary SCell (PSCell)) through an offset), event A4 (indicating that the neighboring cell becomes better than the threshold), or event A5 (the serving cell becomes worse than the first threshold while the neighboring cell becomes better than the second threshold). In another example, the measurement results can include the value of the signal strength or quality of cell 126 (e.g., reference signal received power (RSRP), reference signal received quality (RSRQ), or signal-to-noise ratio (SINR)). In response to determining that the measurement results indicating the signal strength or quality of cell 126 meet the threshold, base station 104 decides to hand over UE 102 to base station 106. In response to the handover decision, base station 104 decides to release the SRB4 configuration before handing over UE 102 to base station 106. In some implementations, the offset and / or threshold can be predetermined by base station 104. In some implementations, base station 104 can send the offset and / or threshold to UE 102.

[0087] In another implementation, the measurement result indicates that the signal strength or quality of cell 124 does not meet the threshold. For example, the measurement result may include an event identifier indicating an event. The event may be event A2 (indicating that the serving cell becomes worse than the threshold). In another example, the measurement result may include the value of the signal strength or quality of cell 124 (e.g., RSRP, RSRQ, or SINR). In response to determining that the measurement result indicating the signal strength or quality of cell 124 does not meet the threshold, base station 104 decides to release SRB4 and hand over UE 102 to base station 106 (i.e., always release SRB4 during handover). In some implementations, the threshold may be predetermined by base station 104. In some implementations, base station 104 may send the threshold to UE 102.

[0088] In other implementations, if the SRB4 release condition is similar but not the same as the handover condition, base station 104 may determine that it should release SRB4. For example, referring to Figure 7B , when base station 104 receives an indication that the measurement result of cell 124 at UE 102 meets a first predetermined threshold but does not meet a second predetermined threshold, base station 104 determines that 715 the measurement result meets the SRB4 release condition but does not meet the handover condition. In this scenario, base station 104 sends a 737 RRC reconfiguration message to UE 102. If base station 104 subsequently determines that 716 the measurement result meets the second predetermined threshold, base station 104 determines that the measurement result now meets the handover condition and subsequently sends a 714 handover request message to base station 106.

[0089] In one implementation, base station 104 receives a first measurement result indicating that the signal strength or quality of cell 124 is lower than a first predetermined threshold and has not yet been lower than a second predetermined threshold. Based on the first measurement result, base station 104 determines that UE 102 may be leaving the coverage area of base station 104. In response to this determination, base station 104 decides to release the SRB4 configuration. Subsequently, base station 104 receives a second measurement result indicating that the signal strength or quality of cell 124 is lower than the second predetermined threshold. Based on the second measurement result, base station 104 decides to hand over UE 102 to base station 106. For example, the first measurement result may include a first event identifier indicating a first event. The first event may be event A2 (indicating that the serving cell becomes worse than the first predetermined threshold). The second measurement result may include a second event identifier indicating a second event. The second event may be event A2 (indicating that the serving cell becomes worse than the second predetermined threshold). In some implementations, base station 104 may send the first predetermined threshold and / or the second predetermined threshold to UE 102.

[0090] In another implementation, the base station 104 receives a first measurement result indicating that the signal strength or quality of cell 124 does not meet a first predetermined threshold. Based on the first measurement result, the base station 104 determines that the UE 102 may be leaving the coverage area of the base station 104. In response to this determination, the base station 104 decides to release the SRB4 configuration. Subsequently, the base station 104 receives a second measurement result indicating that the signal strength or quality of cell 126 is higher than a second predetermined threshold. Based on the second measurement result, the base station 104 decides to hand over the UE 102 to the base station 106. For example, the first measurement result may include a first event identifier indicating a first event. The first event may be event A2 (indicating that the serving cell has become worse than the first predetermined threshold). The second measurement result may include a second event identifier indicating a second event. The second event may be event A2 (indicating that the serving cell has become worse than the second predetermined threshold). In some implementations, the base station 104 may send the first predetermined threshold and / or the second predetermined threshold to the UE 102.

[0091] Therefore, in the scenario shown in Figure 7A and 7B the base station 104 can determine to release SRB4 based on the measurement results indicating the signal strength or quality of cell 124 or cell 126. When releasing SRB4, the base station 104 prevents radio bearer incapability problems that may occur when the base station 106 does not recognize at least one configuration (e.g., the SRB4 configuration) associated with the connection between the UE 102 and the base station 104. As another example, the base station 104 may release SRB4 because the base station 106 is operated by a different vendor than the base station 104.

[0092] In some implementations, after sending a 737 RRC reconfiguration message to the UE 102, the base station 104 sends a 714 handover request message to the base station 106. In other implementations, the base station 104 sends a 714 handover request message to the base station 106 before sending the RRC reconfiguration message 737 to the UE 102. In other implementations, the base station 104 sends a handover request message to the base station 106 and a RRC reconfiguration message to the UE 102 simultaneously.

[0093] In response to the handover request message, the base station 106 may send a 717a handover request confirmation message to the base station 104.

[0094] In response to receiving the 737 RRC reconfiguration message, UE 102 sends a 739 RRC reconfiguration complete message (e.g., RRCConnectionReconfigurationComplete message, RRCReconfigurationComplete message) to base station 104, thereby completing the release of SRB4. Base station 104 may, before receiving a handover request confirmation message (which includes a handover command message) from base station 106 (i.e., as shown in the scenario of Figure 7B ), after receiving a handover request confirmation message from base station 106 ( Figure 7B not shown herein), depending on the relative completion times at UE 102 and base station 106, or after receiving a handover request confirmation message from base station 106 (i.e., as shown in the scenario of Figure 7A ), receive the RRC reconfiguration complete message from UE 102.

[0095] In response to receiving the RRC reconfiguration complete message (i.e., as shown in the scenario of Figure 7A ), before receiving the RRC reconfiguration complete message ( Figure 7A not shown herein), or after receiving the RRC reconfiguration complete message (i.e., as shown in the scenario of Figure 7B ), base station 104 sends a handover command message 719 to UE 102.

[0096] In response to receiving the 719 handover command message, UE 102 sends a 726 handover complete message (e.g., RRCConnectionReconfigurationComplete message, RRCReconfigurationComplete message) to base station 106, thereby completing the handover scenario. Thus, UE 102 operates in a connected state with base station 106 at 728.

[0097] Since base station 104 causes UE 102 to release SRB4 that may not be supported by base station 106, base station 106 avoids providing UE 102 with a configuration that may conflict with the released SRB4. That is, if base station 106 determines to configure UE 102 with a DRB configuration or a new SRB4 configuration associated with the same logical channel identity value as the released SRB4 configuration (included in the handover command message or separately in the RRC reconfiguration message, similar to event 232), then UE 102 verifies the handover command message or the RRC reconfiguration message because the logical channel identity value associated with the DRB configuration or the new SRB4 configuration is not associated with the released SRB4 configuration.

[0098] Now turning to Figure 8, at the start of scenario 800, UE 102 and base stations 104, 106 proceed to events 811, 812, 814, 817, 819, 825, 826, and 827, similar to events 211, 212, 214, 217, 219, 225, 226, and 227.

[0099] In some embodiments, after a handover scenario is successfully completed, base station 106 determines 816 to omit SRB4 support for UE 102. Base station 106 omits the SRB4 support indication when broadcasting 832 system information to UE 102 and other UEs in wireless communication system 100. In response, UE 102 and base station 106 proceed to events 822, 824, 828, and 830, similar to events 222, 224, 328, and 330.

[0100] In other embodiments, in response to a handover request message, base station 106 determines 817 to include an SRB4 support indication for UE 102. Base station 106 includes the SRB4 support indication when broadcasting 833 system information to UE 102 and other UEs in wireless communication system 100. In response, UE 102 and base station 106 proceed to events 823, 828, and 830, similar to events 323, 328, and 330.

[0101] Although base station 104 is shown in Figures 2A - 2B and Figures 3 - 8 as sending a handover request (events 214, 214, 314, 414, 514, 614, 714) and receiving a handover request confirmation message (events 218, 217, 318, 418, 518, 617, 717), base station 104 may alternatively send a handover required message and receive a handover confirmation message. Specifically, base station 104 may send a handover required message to CN 110 (e.g., access management function (AMF) and / or mobility management entity (MME)) instead of sending a handover request message to base station 106. In response, CN 110 may send a handover request message to base station 106, which may in turn include a handover command message in the handover request confirmation message and send the handover request confirmation message to CN 110. CN 110 may in turn include the handover command message in the handover confirmation message and send the handover confirmation message to base station 104.

[0102] Figures 9 - 13 An example message flow diagram of a reconstruction scenario between UE 102 and base stations 104, 106 in wireless communication system 100 is generally shown.

[0103] Now turning to Figure 9, at the start of scenario 900, UE 102 and base station 104 perform a 911 measurement procedure, similar to event 211 discussed above.

[0104] After a period of time, UE 102 detects a radio link failure (RLF) on the established connection with base station 104, or other failures (e.g., a failure in the handover procedure between base stations 104, 106, a failure in reconfiguring SRB4), by receiving a message from base station 104 or base station 106. After detecting the failure, UE 102 then selects base station 106 for serving by performing a 913 RRC connection reestablishment procedure with base station 106. In scenario 900, base station 106 does not support SRB4. After successfully performing the RRC connection reestablishment procedure, UE 102 operates in the connected state with base station 106 at 927. Subsequently, base station 106 performs a reconfiguration procedure 935 similar to event 235, and thus causes UE 102 to release the previously configured SRB4 maintained by base station 104 and apply the DRB configuration provided by base station 106. Therefore, UE 102 operates in the connected state with base station 106, so that UE102 and base station 106 can exchange data via the logical channel identities mapped to the DRB.

[0105] In some embodiments, base station 106 may perform a 935 reconfiguration procedure before UE 102 completes the 913 RRC connection reestablishment procedure (i.e., base station 106 sends an RRC reconfiguration message to UE 102 after sending an RRC connection reestablishment message to UE 102 and before receiving an RRC connection reestablishment complete message from UE 102).

[0106] Now turning to Figure 10 , at the start of scenario 1000, UE 102 and base stations 104, 106 proceed to events 1011, 1012, 1013, and 1027, similar to events 911, 912, 913, and 927.

[0107] In some embodiments, base station 106 proceeds to an event 1016 similar to event 316, and then sends an RRC reconfiguration message 1032 to UE 102 that includes a full configuration or an incremental configuration and omits the SRB4 configuration, similar to event 232. In response, UE 102 proceeds to events 1022 and 1024, similar to events 322, 324.

[0108] In other embodiments, base station 106 proceeds to an event 1017 similar to event 317, and then sends an RRC reconfiguration message 1033 to UE 102 that includes a full configuration or an incremental configuration and includes the SRB4 configuration, similar to event 232. In response, UE 102 proceeds to an event 1023 similar to event 323.

[0109] In response to the application of 1024 DRB configuration or reconfiguration of 1023 SRB, UE 102 sends 1034 RRC connection reconfiguration complete to base station 106, similar to event 234. Accordingly, UE 102 operates 1028 in a connected state with base station 106 via DRB or SRB, and thus UE 102 and base station 106 can communicate 1030 via DRB or SRB, similar to events 328 and 330.

[0110] Now turning to Figure 11 , at the start of scenario 1100, UE 102 and base stations 104, 106 proceed to events 1111, 1112, 1113, and 1127, similar to events 911, 912, 913, and 927.

[0111] In some embodiments, base station 106 proceeds to event 1116 similar to event 416 and subsequently sends 1132 an RRC reconfiguration message to UE 102 omitting the SRB4 configuration indication, similar to event 232. In response, UE 102 proceeds to events 1122 and 1124 similar to events 422 and 424.

[0112] In other embodiments, base station 106 determines 1117 that includes an SRB4 configuration for UE 102. Base station 106 includes the SRB4 configuration in the RRC reconfiguration message and subsequently sends 1133 the RRC reconfiguration message to UE 102, similar to event 232. In response, UE 102 reconfigures 1123 SRB4.

[0113] In response to the application of 1124 DRB configuration or reconfiguration of 1123 SRB, UE 102 sends 1134 RRC connection reconfiguration complete to base station 106, similar to event 234. Accordingly, UE 102 operates 1128 in a connected state with base station 106 via DRB or SRB, and thus UE 102 and base station 106 can communicate 1130 via DRB or SRB, similar to events 328 and 330.

[0114] Now turning to Figure 12 , at the start of scenario 1200, UE 102 and base stations 104, 106 proceed to events 1211, 1212, 1213, and 1227, similar to events 911, 912, 913, and 927.

[0115] In some embodiments, the base station 106 proceeds to an event 1216 similar to event 516 and then sends 1232 an RRC reconfiguration message to the UE 102 that includes an SRB4 release indication or omits an SRB4 retention indication, similar to event 232. In response, the UE 102 proceeds to events 1222 and 1224, similar to events 522, 524.

[0116] In other embodiments, the base station 106 proceeds to an event 1217 similar to event 517 and then sends 1233 an RRC reconfiguration message to the UE 102 that omits an SRB4 release indication or includes an SRB4 retention indication, similar to event 232. In response, the UE 102 proceeds to an event 1223 similar to event 523.

[0117] In response to applying 1224 a DRB configuration or reconfiguring 1223 an SRB, the UE 102 sends 1234 an RRC connection reconfiguration complete to the base station 106, similar to event 234. Accordingly, the UE 102 operates 1228 in a connected state with the base station 106 via a DRB or an SRB, and thus the UE 102 and the base station 106 can communicate 1230 via the DRB or the SRB, similar to events 528 and 530.

[0118] Now turning to Figure 13 , at the start of scenario 1300, the UE 102 and the base stations 104, 106 proceed to events 1311, 1312, and 1313, similar to events 911, 912, and 913. After successfully executing an RRC connection reestablishment procedure, the UE 102 proceeds to events 1322, 1324, and 1328 similar to events 622, 624, and 628. Accordingly, the UE 102 automatically releases SRB4 in response to an RRC connection reestablishment procedure or after the reestablishment scenario is complete.

[0119] Figures 14 - 18 and Figures 19A - 19C generally shows an example message flow diagram of a reselection scenario between the UE 102 and the base stations 104, 106 of the wireless communication system 100.

[0120] Now turning to Figure 14, at the start of scenario 1400, UE 102 and base station 104 perform a 1411 measurement procedure, similar to event 211. After a period of time, base station 104 may detect that there has been below-threshold or no data activity for UE 102 during some time intervals on the established connection. Once detected, base station 104 instructs UE 102 to enter the inactive state of the RAT protocol (e.g., EUTRA-RRC INACTIVE, NR-RRC INACTIVE) by sending a 1401 RRC inactive message (e.g., RRCConnectionRelease message or RRCRelease message) to UE 102. In some embodiments, the RRCConnectionRelease message includes an rrc-InactiveConfig field, and the RRCRelease message includes a suspendConfig field.

[0121] In response to the RRC inactive message, UE 102 enters the 1403 inactive state.

[0122] At some later point in time, such as when UE 102 has moved to a different coverage area and has payload data to send to the wireless communication system 100, UE 102 (in the inactive state) selects or reselects base station 106 for serving by performing a 1405 (re)selection procedure. After UE 102 selects or reselects base station 106, UE 102 determines to perform a 1407 RRC connection resume procedure with base station 106, such as by sending a NAS message to base station 106 or performing a RAN notification area (RNA) update. UE 102 sends a 1426 RRC resume request message (e.g., RRCConnectionResumeRequest message or RRCResumeRequest message) to base station 106.

[0123] In response, base station 106 determines to configure UE 102 with a DRB configuration associated with the same logical channel identity value as the configured SRB4, similar to event 216, because base station 106 does not support or otherwise does not know the configured SRB, or because base station 106 supports the configured SRB4 but intends to release the configured SRB4 (i.e., thus the logical channel identity value assigned to the configured SRB4 can be appropriately used by base station 106). Base station 106 includes the configuration for the DRB in the RRC resume message (e.g., RRCConnectionResume message or RRCResume message) and then sends the RRC resume message 1432 to UE 102.

[0124] The RRC Resume message causes the UE 102 to release SRB4 1422 and apply the DRB configuration indicated in the 1424 RRC Resume message, similar to events 222 and 224. Thus, advantageously, the UE 102 verifies the RRC Resume message because the logical channel identity value associated with the DRB configuration is only associated with the DRB configuration and not with the SRB4 configuration. In some embodiments, the UE 102 may also release the measurement configuration provided by the base station 104 at event 1411.

[0125] Next, the UE 102 sends a 1434 RRC Resume Complete message (e.g., RRCConnectionResumeComplete message, RRCResumeComplete message) to the base station 106, thereby successfully completing the reselection scenario. Thus, the UE 102 operates 1428 in a connected state with the base station 106, and thus the UE 102 and the base station 106 can exchange 1430 data via the logical channel identity mapped to the DRB, similar to events 228 and 230.

[0126] Although Figure 14 it is shown that event 1416 occurs before the UE 102 completes the RRC connection resume procedure, in some embodiments, the base station 106 may determine 1416 to configure the UE 102 with a DRB configuration associated with the same logical channel identity value as the configured SRB4 after the UE 102 completes the RRC resume procedure (i.e., after the base station 106 sends the 1432 RRC Resume message or receives the 1434 RRC Resume Complete message), similar to Figure 2B event 216 of the reconfiguration procedure shown in. Subsequently, the base station 106 may execute the remainder of the reconfiguration procedure to cause the UE 102 to release the previously configured SRB4 maintained by the base station 104 and apply the DRB configuration provided by the base station 106.

[0127] Now turning to Figure 15 , at the start of scenario 1500, the UE 102 and the base stations 104, 106 proceed to events 1511, 1501, 1503, 1505, 1507, and 1526, similar to events 1411, 1401, 1403, 1405, 1407, and 1426.

[0128] In some embodiments, the base station 106 proceeds to an event 1516 similar to event 1016 and subsequently sends a 1532 RRC Resume message to the UE 102 that includes a full configuration or an incremental configuration and omits the SRB4 configuration, similar to event 1432. In response, the UE 102 proceeds to events 1522 and 1524 similar to events 1022 and 1024.

[0129] In other embodiments, the base station 106 proceeds to an event 1517 similar to event 1017 and then sends 1533 to the UE 102 an RRC resume message that includes a full configuration or an incremental configuration and includes an SRB4 configuration, similar to event 1432. In response, the UE 102 proceeds to an event 1523 similar to event 1023.

[0130] Although Figure 15 it is shown that event 1516 (or 1517) may occur before the UE 102 completes the RRC connection resume procedure, in other embodiments, the base station 106 may determine 1516, 1517 to configure the UE 102 with a full configuration or an incremental configuration and omit (or include) the SRB4 configuration after the UE 102 completes the RRC resume procedure (i.e., after the base station 106 sends 1532 (or 1533) the RRC resume message or receives 1534 the RRC resume complete message from the UE 102), similar to event 1016 (or 1017), and then, after the UE 102 completes the RRC resume procedure, send to the UE 102 an RRC reconfiguration message that includes a full configuration or an incremental configuration and omits (or includes) the SRB4 configuration, similar to event 1032 (or 1033). In response, the UE 102 proceeds to event 1522 (or 1523).

[0131] In response to applying the 1524 DRB configuration or reconfiguring the 1523 SRB, the UE 102 sends 1534 an RRC resume complete message to the base station 106, similar to event 1434. Accordingly, the UE 102 operates 1528 in a connected state with the base station 106 via the DRB or SRB, and thus the UE 102 and the base station 106 can communicate 1530 via the DRB or SRB, similar to events 1028 and 1030.

[0132] Now turning to Figure 16 , at the start of scenario 1600, the UE 102 and the base stations 104, 106 proceed to events 1611, 1601, 1603, 1605, 1607, and 1626, similar to events 1411, 1401, 1403, 1405, 1407, and 1426.

[0133] In some embodiments, the base station 106 proceeds to an event 1616 similar to event 1116 and then sends 1632 to the UE 102 an RRC resume message that omits the SRB4 configuration, similar to event 1432. In response, the UE 102 proceeds to events 1622 and 1624 similar to events 1122 and 1124.

[0134] In other embodiments, the base station 106 proceeds to an event 1617 similar to event 1117 and then sends to the UE 102 a RRC resume message 1633 including an SRB4 configuration, similar to event 1432. In response, the UE 102 proceeds to an event 1623 similar to event 1123.

[0135] Although Figure 16 it is shown that event 1616 (or 1617) may occur before the UE 102 completes the RRC connection resume procedure, in other embodiments, the base station 106 may determine 1616, 1617 to omit (or include) the SRB4 configuration after the UE 102 completes the RRC resume procedure (i.e., after the base station 106 sends the RRC resume message 1632 (or 1633) or receives the RRC resume complete message 1634 from the UE 102), similar to event 1116 (or 1117), and then, after the UE 102 completes the RRC resume procedure, send to the UE 102 a RRC reconfiguration message omitting (or including) the SRB4 configuration, similar to event 1132 (or 1133). In response, the UE 102 proceeds to event 1622 (or 1623).

[0136] In response to applying the DRB configuration 1624 or reconfiguring the SRB 1623, the UE 102 sends to the base station 106 a RRC resume complete message 1634, similar to event 1434. Thus, the UE 102 operates 1628 in a connected state with the base station 106 via the DRB or SRB, and thus the UE 102 and the base station 106 can communicate 1630 via the DRB or SRB, similar to events 1128 and 1130.

[0137] Now turning to Figure 17 , at the start of scenario 1700, the UE 102 and the base stations 104, 106 proceed to events 1711, 1701, 1703, 1705, 1707 and 1726, similar to events 1411, 1401, 1403, 1405, 1407 and 1426.

[0138] In some embodiments, the base station 106 proceeds to an event 1716 similar to event 1216 and then sends to the UE 102 a RRC resume message 1732 including an SRB4 release indication or omitting an SRB4 retention indication, similar to event 1432. In response, the UE 102 proceeds to events 1722 and 1724 similar to events 1222 and 1224.

[0139] In other embodiments, the base station 106 proceeds to an event 1717 similar to event 1217 and subsequently sends a 1733 RRC resume message to the UE 102 that omits the SRB4 release indication or includes an SRB4 retention indication, similar to event 1432. In response, the UE 102 proceeds to an event 1723 similar to event 1223.

[0140] Although Figure 17 it is shown that event 1716 (or 1717) may occur before the UE 102 completes the RRC connection resume procedure, in other embodiments, the base station 106 may determine 1716, 1717 to include (or omit) the SRB4 release indication or omit (or include) the SRB4 retention indication after the UE 102 completes the RRC resume procedure (i.e., after the base station 106 sends the 1732 (or 1733) RRC resume message or receives the 1734 RRC resume complete message from the UE 102), similar to event 1216 (or 1217), and subsequently send an RRC reconfiguration message including (or omitting) the SRB4 release indication or omitting (or including) the SRB4 retention indication to the UE 102 after the UE 102 completes the RRC resume procedure, similar to event 1232 (or 1233). In response, the UE 102 proceeds to event 1722 (or 1723).

[0141] In response to applying the 1724 DRB configuration or reconfiguring the 1723 SRB, the UE 102 sends a 1734 RRC resume complete message to the base station 106, similar to event 1434. Thus, the UE 102 operates 1728 in a connected state with the base station 106 via the DRB or SRB, and thus the UE 102 and the base station 106 can communicate 1730 via the DRB or SRB, similar to events 1228 and 1230.

[0142] Now turning to Figure 18 , at the start of scenario 1800, the UE 102 and the base stations 104, 106 proceed to events 1811, 1801, 1803, 1805, and 1807, similar to events 1411, 1401, 1403, 1405, and 1407. In other embodiments, the UE 102 may determine to perform the RRC connection resume procedure after sending the 1826 RRC resume request message to the base station 106 at 1807.

[0143] After successfully executing the RRC connection recovery procedure, UE 102 proceeds to events 1822 and 1824, similar to events 1422 and 1424. Subsequently, UE 102 and base station 106 proceed to events 1826, 1832, 1834, 1828, and 1830, similar to events 1426, 1432, 1434, 1428, and 1430. Accordingly, UE 102 automatically releases SRB4 after the reselection scenario is completed.

[0144] In other embodiments, UE 102 releases SRB4 in response to the RRC connection recovery procedure (e.g., after UE 102 receives the 1832 RRC resume message from base station 106, or after UE 102 sends the 1834 RRC resume complete message to base station 106).

[0145] Now turning to Figure 19A , at the start of scenario 1900, UE 102 and base station 104 execute the 1911 measurement procedure, similar to event 1411. After a period of time, base station 104 may determine that 1913 not only indicates that UE 102 enters the inactive state of the RAT protocol but also releases SRB4. In other words, if the SRB4 release condition is the same as the inactive condition, base station 104 may determine that it should release SRB4. For example, when base station 104 detects that the data activity of UE 102 is below the first threshold within the first time interval on the established connection, the data activity satisfies the inactive condition (and the SRB4 release condition), and accordingly, base station 104 sends a 1937 RRC reconfiguration message (e.g., RRCConnectionReconfiguration message or RRCReconfiguration message) to UE 102, similar to event 737, to cause UE 102 to release 1922 SRB4. After releasing SRB4, UE 102 sends a 1939 RRC reconfiguration complete message (e.g., RRCConnectionReconfigurationComplete message, RRCReconfigurationComplete message) to base station 104, similar to event 739, thereby completing the release of SRB4. In addition, base station 104 sends a 1901 RRC inactive message to UE 102 to indicate that UE 102 enters the inactive state of the RAT protocol (e.g., EUTRA - RRC INACTIVE, NR - RRC INACTIVE), similar to event 1401.

[0146] In other implementations, if the SRB4 release condition is similar but not the same as the inactive condition, base station 104 determines to release SRB4. For example, referring to Figure 19B, when the base station 104 detects that the data activity of the UE 102 on the established connection is lower than the first threshold in the first time interval and higher than the second threshold in the second time interval (where the second time interval can be shorter than the first time interval), the base station 104 determines that the data activity satisfies the SRB4 release condition but does not satisfy the inactivity condition, and accordingly, the base station 104 sends a 1937 RRC reconfiguration message to the UE 102, similar to event 737, to cause the UE 102 to release the 1922 SRB4. After releasing the SRB4, the UE 102 sends a 1939 RRC reconfiguration complete message (e.g., RRCConnectionReconfigurationComplete message, RRCReconfigurationComplete message) to the base station 104, similar to event 739, thus successfully completing the release of the SRB4. If the base station 106 subsequently detects that the data activity of the UE 102 is lower than the second threshold within the second time interval on the established connection, the base station 104 determines that the data activity satisfies the inactivity condition, and accordingly, the base station 104 sends a 1901 RRC inactivity message to the UE 102, similar to event 1401, to indicate that the UE 102 enters the inactivity state of the RAT protocol (e.g., EUTRA-RRC INACTIVE, NR-RRC INACTIVE).

[0147] Now refer to Figure 19C the scenario where, when the base station 104 in another implementation determines that the data activity satisfies the inactivity condition (as well as the SRB4 release condition), the base station 104 may send a 1938 RRC inactivity message (e.g., RRCConnectionRelease message or RRCRelease message) to the UE 102, contrary to Figure 19A event 1937, and similar to Figure 14 event 1401 in

[0148] Now refer to Figure 19A , Figure 19B and Figure 19CAfter the UE 102 receives the RRC Inactive message, the UE 102 and the base stations 104, 106 proceed to events 1903, 1905, 1907, and 1926, similar to events 1403, 1405, 1407, and 1426.

[0149] In response to the RRC Resume Request message, the base station 106 sends a Retrieve UE Context Request message 1941 to the base station 104 to retrieve the UE context of the UE 102. In response, the base station 104 sends a Retrieve UE Context Response message 1943 including the UE context. In response to the Retrieve UE Context Response message, the base station 106 sends an RRC Resume message 1932 to the UE 102, similar to event 1432. In response, the UE 102 operates 1928 in a state connected to the base station 106 and sends an RRC Resume Complete message 1934 (e.g., an RRCConnectionResumeComplete message or an RRCResumeComplete message) to the base station 106, thus successfully completing the reselection scenario.

[0150] Since the base station 104 causes the UE 102 to release the SRB4 that the base station 106 may not support, in event 1943, the base station 106 does not receive the SRB4 configuration from the base station 104 and further avoids providing a configuration to the UE 102 that may conflict with the released SRB4. That is, if the base station 106 determines to configure the UE 102 with a DRB configuration or a new SRB4 configuration associated with the same logical channel identity value as the released SRB4 (included in the RRC Resume message in event 1932 or included separately in an RRC Reconfiguration message, similar to event 232), the UE 102 verifies the RRC Resume message or the RRC Reconfiguration message because the logical channel identity value associated with the DRB configuration or the new SRB4 configuration is not associated with the released SRB4 configuration.

[0151] Figures 20 - 22 An example message flow diagram for managing radio bearers in view of a specific trigger event is generally shown.

[0152] Now turning to Figure 20 , in view of including and / or excluding a specific type of configuration indication, method 2000 releases or reconfigures SRB4, which can be implemented in Figure 1 the base stations 104, 106.

[0153] Method 2000 begins at block 2002, where a first base station (e.g., base station 104) sends a first message (e.g., an RRC Reconfiguration message) including an SRB4 configuration to a UE (e.g., UE 102) ( Figure 2A event 206).

[0154] In block 2004, a second base station (e.g., base station 106) determines to send a second message (e.g., a handover command message, an RRC reconfiguration message, an RRC resume message) to configure the UE for events 220, 232, 320, 321, 420, 520, 521, 619, 1032, 1033, 1132, 1133, 1232, 1233, 1432, 1532, 1533, 1632, 1633, 1732, and 1733). Figures 2A - 2B and Figures 3 - 6 and Figures 10 - 12 and Figures 14 - 17 and

[0155] In block 2006, if the second base station determines to request the UE to release the SRB, then in block 2008, the second base station may (i) include in the second message an indication of the DRB configuration associated with the same logical identifier as the SRB4 configuration for events 216, 935, and 1416; and / or (ii) include in the second message a full configuration or an incremental configuration and omit the SRB4 configuration for events 316, 1016, and 1516; and / or (iii) omit the SRB4 configuration in the second message for events 416, 1116, and 1616; and / or (iv) include an SRB4 release indication in the second message for events 516, 1216, and 1716; and / or (v) omit the SRB4 retention indication in the second message for events 516, 1216, and 1716. Figures 2A - 2B and Figure 9 and Figure 14 and Figure 3 and Figure 10 and Figure 15 and Figure 4 and Figure 11 and Figure 16 and Figure 5 and Figure 12 and Figure 17 and Figure 5 and Figure 12 and Figure 17 and

[0156] If the second base station determines to request the UE to reconfigure the SRB4, then in block 2010, the second base station may (i) include in the second message a full configuration or an incremental configuration and the SRB4 configuration for events 317, 1017, and 1517; and / or (ii) include the SRB4 configuration in the second message for events 1117 and 1617; and / or (iii) omit the SRB4 release indication in the second message for events 56, 57, and 58. Figure 3 and Figure 10 and Figure 15 and Figure 11 and Figure 16 and Figure 5 and Figure 12 andFigure 17 Events 517, 1217, and 1717); and / or (iv) including an SRB4 retention indication in the second message ( Figure 5 , Figure 12 and Figure 17 Events 517, 1217, and 1717).

[0157] Now turning to Figure 21 , in view of the types of procedures that can be implemented in the Figure 1 UE 102 or base station 104, method 2100 automatically releases SRB4.

[0158] Method 2100 begins at block 2102, where a first base station (e.g., base station 104) transmits a first message (e.g., an RRC reconfiguration message) including an SRB4 configuration, and the UE (e.g., UE 102) receives the first message ( Figure 2A Event 206).

[0159] At block 2104, the first base station or the UE executes a procedure. For example, as Figure 6 shown, base station 104 executes a handover procedure at event 612. As Figure 13 shown, UE 102 executes an RRC connection reestablishment procedure at event 1313. As Figure 18 shown, UE 102 executes an RRC connection resume procedure.

[0160] At block 2106, if the first base station or the UE executes at least one of a handover procedure, an RRC connection reestablishment procedure, or an RRC connection resume procedure, then at block 2108 the UE automatically releases SRB4 ( Figure 6 , Figure 13 and Figure 18 Events 622, 1322, and 1822). Otherwise, method 2100 ends or returns to block 2102.

[0161] Now turning to Figure 22 , method 2200 releases or reconfigures SRB4 in view of including and / or excluding a specific type of indication in the system information, which can be implemented in the Figure 1 UE 102 or base stations 104, 106.

[0162] Method 2200 begins at block 2202, where a first base station (e.g., base station 104) transmits a first message (e.g., an RRC reconfiguration message) including an SRB4 configuration, and the UE (e.g., UE 102) receives the first message ( Figure 2A Event 206).

[0163] At block 2204, after the first base station successfully executes a handover procedure such that the UE establishes a connection with a second base station (e.g., base station 106), the second base station transmits or broadcasts system information, and the UE receives the system information ( Figure 8 events 832, 833).

[0164] At block 2206, if the second base station determines to omit the SRB4 support indication in the system information, then at block 2208 the UE releases SRB4 ( Figure 8 event 822). At block 2206, if the second base station determines to include the SRB4 support indication in the system information, then at block 2210 the UE reconfigures SRB4 ( Figure 8 event 823).

[0165] Now turning to Figure 23 , method 2300 releases SRB4 in view of whether an SRB4 release condition is met, which can be implemented in Figure 1 base station 104.

[0166] Method 2300 begins at block 2302, where a first base station (e.g., base station 104) transmits a first message (e.g., an RRC reconfiguration message) including an SRB4 configuration, similar to blocks 2002, 2102, and 2202 ( Figure 2A , Figure 7A , Figure 7B , Figure 19A , Figure 19B and Figure 19C events 206, 711, 1911).

[0167] At block 2304, the first base station detects that the SRB4 release condition is met (and optionally, at block 2307, detects whether a handover condition or an inactivity condition is also met) ( Figure 7A , Figure 7B , Figure 19A , Figure 19B , Figure 19C events 713, 715, 1913, 1915). At block 2307, the first base station can continue to perform the detection until the first base station detects that a handover condition or an inactivity condition is met.

[0168] In response, the first base station sends a message (e.g., an RRC reconfiguration message, an RRC inactivity message) to the UE (e.g., UE 102) at block 2306 to cause the UE to release SRB4 ( Figure 7A , Figure 7B , Figure 19A , Figure 19B and Figure 19C events 737, 1937, 1938).

[0169] In some embodiments, when the first base station at block 2307 optionally detects whether a handover condition or an inactivity condition is met, the first base station may determine at block 2308, after block 2306, that the handover condition is met and may continue to determine at block 2312 to hand over the UE to the second base station (e.g., base station 106)( Figure 7B event 716). At block 2308, the first base station may continue to perform the detection until the first base station detects that the handover condition is met.

[0170] Alternatively, the first base station may alternatively determine at block 2310, after block 2306, that the inactivity condition is met and may continue to determine at block 2314 to indicate that the UE enters the inactivity state( Figure 19B event 1916). At block 2310, the first base station may continue to perform the detection until the first base station detects that the inactivity condition is met.

[0171] Figure 24 depicts an example method 2400 for managing radio bearers that may be implemented in the Figure 1 RAN 108, which includes a first base station 104 that supports a first type of radio bearer and a second base station 106 that does not support the first type of radio bearer.

[0172] Method 2400 begins at block 2402, where the RAN determines that a UE (e.g., UE 102) configured with a first radio bearer of the first type will obtain a radio connection to the second base station( Figures 2A - 2B and Figures 3 - 18 events 212, 312, 412, 512, 612, 713, 716, 812, 913, 1013, 1113, 1213, 1313, 1405, 1505, 1605, 1705, and 1805), and this radio bearer terminates at the first base station. Subsequently, the RAN sends a message at block 2404 to cause the UE to release the first radio bearer and establish a second radio bearer of the second type that terminates at the second base station( Figures 2A - 2B and Figures 3 - 18 events 218, 220, 232, 318, 320, 418, 420, 518, 520, 617, 619, 832, 935, 1032, 1132, 1232, 1313, 1432, 1532, 1632, 1732, 1807).

[0173] Figure 25 depicts an example method 2500 for managing radio bearers, which may be implemented in the Figure 1 UE 102.

[0174] Method 2500 begins at block 2502, where the UE communicates with a first base station via a first radio bearer associated with a dedicated control channel and configured to carry at least application layer measurement report information, the radio bearer being associated with a logical channel identity ( Figures 2A - 2B and Figures 3 - 18 、 Figures 19A - 19C events 211, 311, 411, 511, 611, 711, 811, 911, 1011, 1111, 1211, 1311, 1411, 1511, 1611, 1711, 1811 and 1911). Subsequently, at block 2504, the UE receives a message from the RAN including the first base station and a second base station related to (i) the first radio bearer or (ii) a second radio bearer having the logical channel identity and terminating at the second base station ( Figures 2A - 2B and Figures 3 - 18 、 Figures 19A - 19C events 218, 220, 232, 318, 320, 319, 321, 418, 420, 518, 520, 617, 619, 737, 832, 833, 935, 1032, 1033, 1132, 1133, 1232, 1233, 1313, 1432, 1532, 1533, 1632, 1633, 1732, 1733 and 1807, 1937 and 1938). In response to the message, the UE releases or reconfigures the first radio bearer at block 2506 ( Figures 2A - 2B and Figures 3 - 18 、 Figures 19A - 19C events 222, 322, 323, 422, 522, 523, 622, 722, 822, 823, 935, 1022, 1023, 1122, 1123, 1222, 1223, 1322, 1422, 1522, 1523, 1622, 1623, 1722, 1723 and 1822 and 1922).

[0175] The following additional considerations apply to the above discussion.

[0176] A user equipment (e.g., UE 102) in which the technology of the present disclosure can be implemented can be any suitable device capable of wireless communication, such as a smart phone, a tablet computer, a laptop computer, a mobile gaming console, a point of sale (POS) terminal, a health monitoring device, a drone, a camera, a media streaming dongle or other personal media devices, a wearable device such as a smart watch, a wireless hotspot, a femtocell or a broadband router. In addition, the user equipment can be embedded in an electronic system in some cases, such as a head unit of a vehicle or an advanced driver assistance system (ADAS). Further still, 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 can include one or more general-purpose processors, computer-readable memories, user interfaces, one or more network interfaces, one or more sensors, etc.

[0177] Certain embodiments described in the present disclosure include logic or several components or modules. A module can be a software module (e.g., 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 certain operations and can be configured or arranged in a certain manner. A hardware module can include configured dedicated circuitry or logic (e.g., as a dedicated processor, such as a field programmable gate array (FPGA), an application specific integrated circuit (ASIC), or a digital signal processor (DSP)) to perform certain operations. A hardware module can also include programmable logic or circuitry (e.g., as included in a general-purpose processor or other programmable processor) that is temporarily configured by software to perform certain operations. The decision to implement a hardware module in dedicated and permanent circuitry or in temporarily configured circuitry (e.g., configured by software) can be driven by cost and time considerations.

[0178] 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. The software can be executed by one or more general-purpose processors or one or more dedicated processors.

[0179] After reading the present disclosure, those skilled in the art will appreciate that there are still additional and alternative structural and functional designs for managing electrical carriers through the principles disclosed herein. Therefore, although specific embodiments and applications have been shown and described, it should be understood that the disclosed embodiments are not limited to the exact structures and components disclosed herein. Various modifications, variations, and alterations to the arrangements, operations, and details of the methods and devices disclosed herein can be made without departing from the spirit and scope defined in the appended claims, which will be apparent to those of ordinary skill in the art.

[0180] Aspect 1. A method for managing radio bearers in a UE, the method comprising: communicating, by processing hardware, with a first base station via a first radio bearer associated with a dedicated control channel and configured to carry at least application layer measurement report information, the first radio bearer being associated with a logical channel identifier; receiving, by the processing hardware, from a radio access network (RAN) including the first base station and a second base station, a message related to (i) the first radio bearer or (ii) a second radio bearer having the logical channel identifier and terminating at the second base station; and releasing or reconfiguring, by the hardware, the first radio bearer in response to the message.

[0181] Aspect 2. The method according to aspect 1, wherein: the message is associated with one of (i) a handover procedure, (ii) a procedure for reconstructing a radio connection, or (iii) a procedure for resuming a previously suspended radio connection; and the method comprises releasing the first radio bearer in response to the message.

[0182] Aspect 3. The method according to aspect 2, wherein the message includes a configuration for the second radio bearer.

[0183] Aspect 4. The method according to aspect 2, wherein the message does not include a configuration for the first radio bearer.

[0184] Aspect 5. The method according to aspect 4, wherein the message includes a complete configuration for the radio link between the UE and the second base station but does not include a configuration for the first radio bearer.

[0185] Aspect 6. The method according to aspect 2, wherein the message includes a dedicated field indicating that the UE is to release the first radio bearer.

[0186] Aspect 7. The method according to aspect 2, wherein the message includes system information related to the second base station, the system information indicating that the second base station does not support the first radio bearer.

[0187] Aspect 8. The method according to any one of aspects 1 - 7, wherein: the message is associated with a protocol for controlling radio resources and indicates that the radio link connection between the UE and the first base station is inactive.

[0188] Aspect 9. The method according to any one of aspects 1 - 7, wherein the message indicates a failure of one of (i) the radio link between the UE and the first base station, (ii) a handover procedure, or (iii) the reconfiguration of the first radio bearer.

[0189] Aspect 10. The method according to aspect 1, wherein: the message includes a complete configuration or an incremental configuration including a configuration for the first radio bearer; the method comprises reconfiguring the first radio bearer according to the complete configuration or the incremental configuration.

[0190] Aspect 11. The method according to any one of the preceding aspects, wherein the message comprises one of the following: (i) a handover command when the message is associated with a handover procedure, or (ii) a reconfiguration command associated with a protocol for controlling radio resources when the message is associated with a procedure for reconstructing a radio connection, or (iii) a resume command associated with a protocol for controlling radio resources when the message is associated with a procedure for resuming a previously suspended radio connection.

[0191] Aspect 12. The method according to aspect 1, further comprising: releasing a first radio bearer in response to determining that the message comprises a configuration for a second radio bearer, the configuration of the second radio bearer specifying a logical channel identifier of the first radio bearer.

[0192] Aspect 13. The method according to any one of the preceding aspects, wherein: the first radio bearer is a signaling radio bearer 4 (SRB4), and the second radio bearer is a data radio bearer (DRB).

[0193] Aspect 14. A user equipment, comprising processing hardware and configured to implement the method according to any one of aspects 1 to 13.

[0194] Aspect 15. A method in a radio access network (RAN), the radio access network comprising a first base station supporting a first type of radio bearer and a second base station not supporting the first type of radio bearer, the method comprising: determining by processing hardware that a user equipment (UE) configured with a first radio bearer of the first type is to obtain a radio connection to the second base station, the radio bearer terminating at the first base station; and sending by processing hardware a message to cause the UE to release the first radio bearer and establish a second radio bearer of a second type terminating at the second base station.

[0195] Aspect 16. The method according to aspect 15, wherein the first type is associated with a dedicated control channel and is configured to carry at least application layer measurement report information.

[0196] Aspect 17. The method as in aspect 16, wherein: the first type is a signaling radio bearer 4 (SRB4), and the second type is a data radio bearer (DRB).

[0197] Aspect 18. The method according to aspect 15, wherein: the message is associated with one of (i) a handover procedure, (ii) a procedure for reconstructing a radio connection, or (iii) a procedure for resuming a previously suspended radio connection; the method comprising releasing the first radio bearer in response to sending the message.

[0198] Aspect 19. The method according to aspect 18, wherein the message comprises a configuration for the second radio bearer.

[0199] Aspect 20. The method according to aspect 18, wherein the message does not include a configuration for the first radio bearer.

[0200] Aspect 21. The method according to aspect 18, wherein the message includes a complete configuration for the radio link between the UE and the second base station, but does not include a configuration for the first radio bearer.

[0201] Aspect 22. The method according to aspect 18, wherein the message includes a dedicated field indicating that the UE is to release the first radio bearer.

[0202] Aspect 23. The method according to aspect 22, further comprising: receiving a measurement report from the UE via a first radio bearer of a first type; determining that the measurement report indicates that a cell level measurement result satisfies a first threshold; and transmitting the message in response to the determination.

[0203] Aspect 24. The method according to aspect 23, wherein the determination further comprises determining that the measurement report indicates that the cell level measurement result does not satisfy a second threshold higher than the first threshold.

[0204] Aspect 25. The method according to aspect 22, further comprising: detecting that data activity on a connection established between the UE and the first base station does not satisfy a first threshold within a first time interval; and transmitting the message in response to the determination.

[0205] Aspect 26. The method according to aspect 25, wherein the detection further comprises detecting that the data activity satisfies a second threshold lower than the first threshold within a second time interval.

[0206] Aspect 27. The method according to aspect 18, wherein the message includes system information related to the second base station, and the system information indicates that the second base station does not support the first radio bearer.

[0207] Aspect 28. The method according to any one of aspects 15 - 27, wherein the message includes one of the following: (i) a handover command when the message is associated with a handover procedure, or (ii) a reconfiguration command associated with a protocol for controlling radio resources when the message is associated with a procedure for re - establishing a radio connection, or (iii) a resume command associated with a protocol for controlling radio resources when the message is associated with a procedure for resuming a previously suspended radio connection.

[0208] Aspect 29. A base station, comprising processing hardware and configured to implement the method according to any one of aspects 15 - 28.

[0209] Aspect 30. A RAN, comprising a first base station and a second base station and configured to implement the method according to any one of aspects 15 - 28.

Claims

1. A method for managing radio bearers in a user equipment (UE), the method comprising: communicating, by the UE, with a first base station on a signaling radio bearer 4 (SRB4), the SRB4 being associated with a dedicated control channel and configured to carry at least application layer measurement report information, and the SRB4 being associated with a logical channel identifier; receiving, by the UE, from a radio access network (RAN) including the first base station and a second base station, a message related to a data radio bearer (DRB), the DRB having the logical channel identifier and terminating at the second base station; and releasing, in response to the message, by the UE, the SRB4.

2. The method according to claim 1, wherein: the message is associated with one of the following: (i) a handover procedure, (ii) a procedure for re-establishing a radio connection, or (iii) a procedure for resuming a previously suspended radio connection.

3. The method according to claim 2, wherein the message includes a complete configuration for a radio link between the UE and the second base station, but does not include a configuration for the SRB4.

4. The method according to claim 2, wherein the message includes a dedicated field indicating that the UE will release the SRB4.

5. The method according to claim 1, wherein: the message includes a complete configuration or an incremental configuration, the complete configuration or the incremental configuration including a configuration for the SRB4; and the method includes reconfiguring the SRB4 according to the complete configuration or the incremental configuration.

6. The method according to claim 1, further comprising: releasing, in response to determining that the message includes a configuration for the DRB, the SRB4, the configuration for the DRB specifying the logical channel identifier of the SRB4.

7. A user equipment, comprising processing hardware and configured to implement the method according to any one of claims 1 to 6.

8. A method in a radio access network (RAN), the radio access network including a first base station supporting a first type of radio bearer and a second base station not supporting the first type of radio bearer, the method comprising: determining, by the RAN, that a user equipment (UE) configured with a signaling radio bearer 4 (SRB4) terminating at the first base station will obtain a radio connection to the second base station, wherein the first type is associated with a dedicated control channel and configured to carry at least application layer measurement report information; and sending, by the RAN, a message to cause the UE to release the SRB4 and establish a data radio bearer (DRB) that terminates at the second base station.

9. The method according to claim 8, wherein: the message is associated with one of the following: (i) a handover procedure, (ii) a procedure for re-establishing a radio connection, or (iii) a procedure for resuming a previously suspended radio connection; and the method includes releasing the SRB4 in response to sending the message.

10. The method according to claim 9, wherein, the message includes a complete configuration for a radio link between the UE and the second base station, but does not include a configuration for the SRB4.

11. The method according to claim 9, wherein, the message includes a dedicated field indicating that the UE will release the SRB4.

12. A RAN includes a first base station and a second base station, and is configured to implement the method according to any one of claims 8-11.

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