Patent Description:
In the <NUM> system, Hybrid FSK and QAM Modulation (FQAM) and sliding window superposition coding (SWSC) as an advanced coding modulation (ACM), and filter bank multi carrier (FBMC), non-orthogonal multiple access (NOMA), and sparse code multiple access (SCMA) as an advanced access technology have been developed.

A Fifth generation (<NUM>) communication system (i.e., New Radio (NR)) is being developed in order to meet a growing need for broadband with Enhanced Mobile Broadband (eMBB) while also supporting new use cases like Ultra-Reliable Low Latency Commination (URLLC) and Massive Machine Type Communication (mMTC). The NR is an orthogonal frequency-division multiplexing (OFDM)-based air interface designed to support a wide variation of <NUM> device-types, services, deployments and spectrum. A network monitors a UE behavior and provides necessary resources to the UE to perform any operation that the UE requires. The operation can be, for example, but not limited to, a data uplink, a data downlink, and calls. A signal strength and quality experienced by the UE varies according to a proximity of the UE with a next generation node B (i.e., gNB). The UE's near a cell are expected to have a better signal condition compared to the ones which are far from the gNB i.e., cell edge situation.

Further, a radio access network (RAN) Node or the gNB in the NR/ an eNB in a Long-Term Evolution (LTE) always maintains a context on the UE that are in an active Radio Resource Connection (RRC) connection with it. At any point of time, the gNB can handover a mobile device/ the UE from its control (i.e., source cell) to another gNB or another cell (i.e., target cell), thus transferring an entire context of the UE to the target cell. This decision is taken by the network optionally based on assistance information received from the UE, with the help of measurement reports about neighbor cells. In other words, the gNB configures the UE to measure the signal condition of the serving cell and neighboring cells that may belong to a different gNB. There is a specific measurement criterion, and a specific reporting criterion, both of which are configured by the serving gNB. Due to various reasons like weak signal condition, heavy load on serving gNB etc., the serving gNB can handover the UE to the neighbor cell or the target gNB and this could be done based on the assistance information received from the UE in form of measurement reports.

In the NR, a conditional handover (CHO) and a conditional PSCell change (CPC) are introduced. In CHO, the network provides a candidate target PCell configurations to the UE first, along with a condition for evaluating these candidates. Once the configured condition is satisfied for any candidate cell, then the conditional handover to this candidate cell is executed. Similarly, for the CPC, a secondary node (SN) provides the candidate target PSCell configurations to the UE first, along with a condition for evaluating these candidates. Once the configured condition is satisfied for any candidate cell, then the conditional PSCell change to this candidate cell is executed.

Thus, it is desired to address the shortcomings or at least provide a useful alternative.

In a discussion paper to <NPL>, topics concerning intra-SN PSCell change without MN involvement in Rel-<NUM>. were discussed in general.

At the same meeting, a change request to TS <NUM> (CR <NUM>), was filed by <NPL>", and concerned with capturing agreements for NR mobility enhancement into stage <NUM> specification.

Still at the same meeting, a change request to TS <NUM>, was filed by <NPL>", and concerned with supporting the conditional NR PSCell change for intra-SN without MN involvement and agreements were made as following in RAN2#107bis meeting.

For a more efficient communication system, there is a need for a method for handle conditional configuration stored in a UE.

The principal object of the embodiments herein is to provide a method for handle conditional configuration stored in a UE and conditional failures, so that the UE does not have an ambiguity about the CHO configuration.

The present disclosure is illustrated in the accompanying drawings, throughout which like reference letters indicate corresponding parts in the various figures. The embodiments herein will be better understood from the following description with reference to the drawings, in which:.

As is traditional in the field, embodiments may be described and illustrated in terms of blocks which carry out a described function or functions. These blocks, which may be referred to herein as managers, units, modules, hardware components or the like, are physically implemented by analog and/or digital circuits such as logic gates, integrated circuits, microprocessors, microcontrollers, memory circuits, passive electronic components, active electronic components, optical components, hardwired circuits and the like, and may optionally be driven by firmware. The circuits may, for example, be embodied in one or more semiconductor chips, or on substrate supports such as printed circuit boards and the like. The circuits constituting a block may be implemented by dedicated hardware, or by a processor (e.g., one or more programmed microprocessors and associated circuitry), or by a combination of dedicated hardware to perform some functions of the block and a processor to perform other functions of the block. Each block of the embodiments may be physically separated into two or more interacting and discrete blocks without departing from the scope of the disclosure. Likewise, the blocks of the embodiments may be physically combined into more complex blocks without departing from the scope of the disclosure.

Accordingly, the embodiments herein provide a method for handling a conditional configuration stored in a UE. The method includes receiving, by the UE, an RRC message indicating a release of a SCG from an MN. Further, the method includes releasing, by the UE, at least one of a stored CPC configuration and a variable storing a CPC configuration in response to receiving the RRC message indicating the release of the SCG.

<FIG> is a sequence diagram illustrating in which a UE (<NUM>) retains a stored CPC configuration and corresponding measurement configuration upon receiving SCG release without CPC release from a network, according to the prior art.

Method to handle the UE stored CPC configuration on event of SCG release.

In the conventional method, for a UE behavior when the UE (<NUM>) configured with a CHO is sent to an RRC_INACTIVE state i.e., the CHO configured UE is sent an RRC release message with suspend configuration which transition the UE state from an RRC_CONNECTED state to an RRC_INACTIVE state is already captured in the specification of the 3GPP TS <NUM> v16. When the RRC release message is received by the UE (<NUM>) with the stored CHO configuration, the UE (<NUM>) may autonomously release the CHO configuration upon entering RRC_INACTIVE state. However, the handling of CPC configuration when SCG is released by the network has not been discussed in the 3GPP specification. Further, it is already agreed that the CPC configuration stored in the UE (<NUM>) is released on successful CPC execution or successful conventional PSCell change.

Similar to the CHO, the UE (<NUM>) stored CPC configuration and the linked measurement configuration is released on successful execution of the CPC or on the successful completion of a conventional PSCell change. The UE (<NUM>) stored conditional configuration is also released on entering the RRC IDLE or the RRC_INACTIVE state. However, with respect to a RAN2, the handling of UE (<NUM>) stored CPC configuration on the event of the SCG release has not been discussed in the 3GPP specification.

The CPC configuration is limited to intra-SN conditional PSCell change and is configured to the UE (<NUM>) by the SN without MN involvement. When the SCG is released, the UE (<NUM>) resets a SCG medium access control (MAC), releases all radio link control (RLC) entities on the SCG and releases a SCG bearer. Only the radio bearer configuration may still be retained. The UE (<NUM>) is now only connected to MCG and the radio bearers may either be released or reconfigured by the MCG. In such a state, there is no benefit from the stored CPC configuration.

As provisioned in current 3GPP specification TS <NUM> v16. <NUM>, the CPC configuration stored in the UE (<NUM>) is retained and not released when the SCG is released. This leads to a scenario where the UE (<NUM>) is no longer in a multi-radio dual connectivity (MR-DC) but still maintains the conditional configuration for the PSCell change. Since simultaneous configuration of the CHO and the CPC cannot be provided to the UE (<NUM>), there is only one variable defined for storing the conditional configuration. Therefore, the received configuration is stored in a common variable i.e., the CPC and the CHO configurations are stored in a VarConditionalConfig. Therefore, the received configuration creates ambiguity to the UE (<NUM>) if the stored CPC configuration is retained after the SCG is released. This may even lead to UE (<NUM>) treating a future CHO configuration from MN (<NUM>) as an invalid configuration because it already has a stored CPC configuration. Therefore, the UE (<NUM>) stored CPC configuration has to be released when the NR SCG is released. Additionally, measID and reportConfig associated with CPC config, and measObject(s) only associated to CPC may be removed when the SCG is released (as explained in the <FIG>).

As shown in the <FIG>, at S102, the RRC connection is established between the UE (<NUM>) and a SN (<NUM>), and a dual connectivity (DC) connection is established between the UE (<NUM>) and the SN (<NUM>). At S104, the SN (<NUM>) sends a CPC candidate configuration to the MN (<NUM>). At S106, an RRC reconfiguration including a CPC configuration container and a CPC condition is shared between the UE (<NUM>) and the MN (<NUM>). At S108, the UE (<NUM>) receives the CPC configuration along with measurement configuration stored in a VarConditionalConfig. At S110, the RRC reconfiguration with the SCG release without a CPC release is shared between the UE (<NUM>) and the MN (<NUM>). At S112, the UE (<NUM>) maintains the stored CPC configuration and associated measurement configuration. At S114, the UE (<NUM>) is connected only to the MN (<NUM>). At S116, as the CPC configuration is stored, ambiguity for the UE about the CHO configuration.

<FIG> is a sequence diagram illustrating a provided method in which the UE (<NUM>) autonomously clears the stored CPC configuration and corresponding measurement configuration upon receiving SCG release without CPC release from the network according to embodiments of the present disclosure.

At S202, the RRC connection is established between the UE (<NUM>) and the SN (<NUM>) and the DC connection is established between the UE (<NUM>) and the SN (<NUM>). At S204, the SN (<NUM>) sends the CPC candidate configuration to the MN (<NUM>). At S206, an RRC reconfiguration including the CPC configuration container and the CPC condition is shared between the UE (<NUM>) and the MN (<NUM>). At S208, the UE (<NUM>) receives the CPC configuration along with measurement configuration stored in the VarConditionalConfig. At S210, the RRC reconfiguration with SCG release without the CPC release is shared between the UE (<NUM>) and the MN (<NUM>). At S212, the UE (<NUM>) autonomously release the stored CPC along with the measurement configuration. At S214, the UE (<NUM>) is connected only to the MN (<NUM>). At S216, the UE (<NUM>) does not have the ambiguity about the CHO configuration.

In an example, when the SCG is released, the UE (<NUM>) autonomously releases the stored CPC configuration. Further, measID and reportConfig associated with the CPC config, and measObject(s) only associated to CPC may be removed by the UE (<NUM>) when SCG is released. The changes to specification for implementing these embodiments are illustrated below.

Meanwhile, the operations of the UE described above are merely examples, and the present disclosure is not limited thereto. That is, some of the above operations may be omitted or may be performed simultaneously.

Release of cell group means only release of the lower layer configuration of the cell group but the RadioBearerConfig may not be released.

Further, there are <NUM> configurations associated to the CHO:.

Upon receiving CHO/CPC configuration, the UE (<NUM>) stores one entry per candidate cell. The entry is identified using the CHO id signaled by BS. Each entry consist of conditional configuration for a candidate, and the associated measurement configuration.

illustrates an overview of a wireless communication system (<NUM>) in which the UE (<NUM>) autonomously removes the stored CPC configuration and corresponding measurement configuration upon receiving SCG release from the MN (<NUM>) according to embodiments of the present disclosure. The wireless communication system (<NUM>) includes the UE (<NUM>) and the MN (<NUM>). The UE (<NUM>) can be, for example, but not limited to a cellular phone, a smart phone, a personal digital assistant (PDA), a tablet computer, a laptop computer, an Internet of Things (IoT), a virtual reality device and an immersive system. The UE (<NUM>) includes a processor (<NUM>), a transceiver (<NUM>), a memory (<NUM>), and a SCG release based event handle controller (<NUM>). The processor (<NUM>) is coupled with the transceiver (<NUM>), the memory (<NUM>) and the SCG release based event handle controller (<NUM>).

The SCG release based event handle controller (<NUM>) is configured to receive the RRC message indicating the release of the SCG from the MN (<NUM>). In an embodiment, the MN (<NUM>) is one of an evolved UMTS terrestrial radio access Network (E-UTRA) and a NR network. In response to receiving the RRC message indicating the release of the SCG, the SCG release based event handle controller (<NUM>) is configured to release a stored CPC configuration and a variable storing a CPC configuration. In an embodiment, the release of the SCG is received without network explicitly asking the UE (<NUM>) to release the stored CPC configuration. In an embodiment, the stored CPC configuration and the variable storing the CPC configuration, on the UE (<NUM>), are released autonomously.

In an embodiment, the SCG release based event handle controller (<NUM>) is configured to detect the measurement identifier associated with the stored CPC configuration and remove the measurement identifier associated with the stored CPC configuration in response to releasing the stored CPC configuration.

In another embodiment, for each of a measurement identifier of a source special cell (SpCell) configuration, the SCG release based event handle controller (<NUM>) is configured to determine whether a report configuration has a report type set to a conditional trigger configuration and remove a report configuration with a matching report configuration identifier from a report configuration list within a VarMeasConfig for a report configuration identifier.

In another embodiment, the SCG release based event handle controller (<NUM>) is configured to remove a measurement object with a matching measurement object identifier (measObjectId) from a measurement object list (measObjectList) within a VarMeasConfig, if a measObjectId is only associated to a report configuration (reportConfig) with a report type set to a conditional trigger configuration (condTriggerConfig). The measurement object can be, for example, but not limited to a frequency to be monitored, a cell list to be monitored, cell information, and frequency offset information.

In another embodiment, the SCG release based event handle controller (<NUM>) is configured to remove a measurement identifier with a matching measurement identifier from a measurement identifier list within a VarMeasConfig.

In another embodiment, the SCG release based event handle controller (<NUM>) is configured to release the measurement object associated with a CPC in response to releasing the stored CPC configuration.

The processor (<NUM>) is configured to execute instructions stored in the memory (<NUM>) and to perform various processes. The transceiver (<NUM>) is configured for communicating internally between internal hardware components and with external devices via one or more networks. The memory (<NUM>) also stores instructions to be executed by the processor (<NUM>). The memory (<NUM>) may include non-volatile storage elements. Examples of such non-volatile storage elements may include magnetic hard discs, optical discs, floppy discs, flash memories, or forms of electrically programmable memories (EPROM) or electrically erasable and programmable (EEPROM) memories. In addition, the memory (<NUM>) may, in some examples, be considered a non-transitory storage medium. The term "non-transitory" may indicate that the storage medium is not embodied in a carrier wave or a propagated signal. However, the term "non-transitory" should not be interpreted that the memory (<NUM>) is non-movable. In certain examples, a non-transitory storage medium may store data that can, over time, change (e.g., in random access memory (RAM) or cache).

Although the <FIG> shows various hardware components of the UE (<NUM>) but it is to be understood that other embodiments are not limited thereon. In other embodiments, the UE (<NUM>) may include less or more number of components. Further, the labels or names of the components are used only for illustrative purpose and does not limit the scope of the disclosure. One or more components can be combined together to perform same or substantially similar function to handle the conditional configuration stored in the UE (<NUM>).

<FIG> are flow charts (S400) illustrating a method for autonomously removing the stored CPC configuration and corresponding measurement configuration upon receiving SCG release from the MN according to embodiments of the present disclosure. The operations (S402-S418) are performed by the SCG release based event handle controller (<NUM>).

At S402, the method includes receiving the RRC message indicating the release of the SCG from the MN (<NUM>). At S404, the method includes releasing the stored CPC configuration and the variable storing the CPC configuration in response to receiving the RRC message indicating the release of the SCG.

In an embodiment, at S406, the method includes removing the measurement object with the matching measurement object identifier from the measurement object list within the VarMeasConfig, if the measObjectId is only associated to the report configuration with the report type set to the conditional trigger configuration.

In another embodiment, at S408, the method includes removing the measurement identifier with the matching measurement identifier from the measurement identifier list within the VarMeasConfig.

In another embodiment, at S410, the method includes releasing the measurement object associated with the CPC in response to releasing the stored CPC configuration.

In another embodiment, at S412, the method includes detecting the measurement identifier associated with the stored CPC configuration. At S414, the method includes removing the at least one measurement identifier associated with the stored CPC configuration in response to releasing the stored CPC configuration.

In another embodiment, at S416, the method includes determining whether the report configuration has the report type set to the conditional trigger configuration for each of measurement identifier of a source special cell (SpCell) configuration. At S418, the method includes removing the report configuration with the matching report configuration identifier from a report configuration list within the VarMeasConfig for a report configuration identifier.

The various actions, acts, blocks, steps, or the like in the flow diagram (S400) may be performed in the order presented, in a different order or simultaneously. Further, in some embodiments, some of the actions, acts, blocks, steps, or the like may be omitted, added, modified, skipped, or the like without departing from the scope of the disclosure.

Method to perform the CHO failure recovery: in the CHO, the UE (<NUM>) may be configured with attemptCondReconfig-r <NUM>. If CHO failure occurs, or a normal handover failure occurs or a radio link failure is detected for the UE (<NUM>) configured with attemptCondReconfig-r160, if the cell selected for recovery while T311 is running belongs to a configured CHO candidate cell, then CHO is triggered to the selected cell. Otherwise, RRC reestablishment is triggered.

Further, there is also a case where the UE (<NUM>) in the NR-DC is configured to perform fast MCG recovery when the RLF is detected or PCell handover has failed. When configured, the UE (<NUM>) sends MCG failure information message via the SCG, to indicate to the network about failure on the MCG. Therefore, there could be a conflict between which procedure to be performed if the UE (<NUM>) is configured with both MCG failure recovery as well as attemptCondReconfig-r16.

One method is to restrict the network from providing both configurations to the UE (<NUM>). Since it is the same network node i.e., MN (<NUM>), that configured these to the UE (<NUM>), it can be ensured by the MN (<NUM>) that both are not simultaneously configured for the UE (<NUM>). However, this is in network control and a mechanism have to be defined on the UE (<NUM>) if both these are configured on the UE (<NUM>) simultaneously. In an embodiment, a CHO based recovery is prioritized and the UE (<NUM>) executes CHO on the selected cell. In this method, the MCG recovery using MCG failure information message is not initiated at all. In another aspect, the UE (<NUM>) is checked if the selection cell belongs to the list of candidate cells configured for the CHO. If selected cell is part of CHO configuration, then CHO is performed i.e., the CHO based recovery is performed. Otherwise, MCG failure recovery is performed i.e., MCG failure information is sent to SCG if the selected cell is not a configured CHO candidate.

Method to perform multiple CPC attempts prior to failure declaration: in most cases, the UE (<NUM>) will be configured with more than one candidate target cell for CPC. Except for T310 expiry i.e., RLF, the other common failures for PSCell change include T304 expiry. The UE (<NUM>) on fulfilling the execution condition(s) for a CPC target cell, initiated execution of CPC. T304 is started, a UE RF tunes to candidate target cell frequency and acquires the cell. Random access is initiated in order to send RRC reconfiguration complete message. If random access is not successful till T304 expiry, failure is declared.

Since there are more than one candidate cells configured to the UE (<NUM>), all these cells belong to the same gNB (i.e., intra-SN cells), it is highly likely that other candidate cells also fulfil the CPC execution condition. In an embodiment, the UE (<NUM>) attempts the CPC execution on all the candidate cells that has fulfilled the execution condition. If CPC execution to all these candidate cells fail, then SCG failure is declared. If CPC execution to any of these cells succeed, then the UE (<NUM>) successfully completes CPC and releases the stored CPC configuration and linked measurement configuration.

The UE (<NUM>) attempts random access to the candidate cell till expiry of T304. However, there is also a maximum number of preamble transmission that is configured to the UE (<NUM>). In an embodiment, the UE (<NUM>) attempts random access for CPC to a candidate cell only for the maximum number of preamble attempts that is configured to the UE (<NUM>). If the random access fails, but T304 is still running, then UE (<NUM>) attempts the CHO execution to the next cell and so on. The SCG failure is declared only when T304 expires and not when access to the first cell fails.

In another embodiment, a method can be used to handle the conditional failures. The method includes checking, by the UE, if a selected cell belongs to a list of candidate cells configured for the CHO. If the selected cell is part of the CHO configuration, then the CHO is performed i.e., the CHO based recovery is performed. Otherwise, an MCG failure recovery is performed i.e., an MCG failure information is sent to the SCG if the selected cell is not a configured CHO candidate.

In another embodiment, a method can be used to perform multiple CPC attempts before declaring SCG failure. The method include the UE (<NUM>) attempting the CPC on all the candidate cells that has fulfilled the execution condition. If the CPC execution to all these candidate cells fail, then the SCG failure is declared. If the CPC execution to any of these cells succeed, then the UE (<NUM>) successfully completes CPC and releases the stored CPC configuration and linked measurement configuration. The method further includes the UE (<NUM>) attempting the random access for CPC to the candidate cell only for the maximum number of preamble attempts that is configured to the UE. If the random access fails, but T304 is still running, then the UE attempts CHO execution to the next cell and so on. SCG failure is declared only when T304 expires and not when access to the first cell fails.

The method can be used to prioritize the CHO based failure recovery over the fast MCG recovery. The method can be used to perform the CHO if the cell selected following MCG failure is the CHO candidate cell, otherwise perform MCG failure recovery. The method can be used to attempt CHO execution on all candidate cells that has fulfilled the execution condition. If access to all cells fail, SCG failure is declared. The method can be used to attempt CPC execution on another candidate that fulfils the execution condition, when maximum preamble attempts have failed on the selected candidate and T304 is still running.

<FIG> illustrates a UE according to embodiments of the present disclosure.

Referring to the <FIG>, the UE (<NUM>) may include a processor (<NUM>), a transceiver (<NUM>) and a memory (<NUM>). However, all of the illustrated components are not essential. The UE (<NUM>) may be implemented by more or less components than those illustrated in <FIG>. In addition, the processor (<NUM>) and the transceiver (<NUM>) and the memory (<NUM>) may be implemented as a single chip according to another embodiment.

The UE (<NUM>) may correspond to UE described above.

The processor (<NUM>) may include one or more processors or other processing devices that control the provided function, process, and/or method. An operation of the UE (<NUM>) may be implemented by the processor (<NUM>). The processor (<NUM>) may control a signal flow between each block to perform the provided function, process, and/or method according to the embodiments of the present disclosure.

The transceiver (<NUM>) may include an RF transmitter for up-converting and amplifying a transmitted signal, and an RF receiver for down-converting a frequency of a received signal. However, according to another embodiment, the transceiver (<NUM>) may be implemented by more or less components than those illustrated in components.

The transceiver (<NUM>) may be connected to the processor (<NUM>) and transmit and/or receive a signal. In addition, the transceiver (<NUM>) may receive the signal through a wireless channel and output the signal to the processor (<NUM>). The transceiver (<NUM>) may transmit a signal output from the processor (<NUM>) through the wireless channel.

The memory (<NUM>) may store the control information or the data included in a signal obtained by the UE (<NUM>). The memory (<NUM>) may be connected to the processor (<NUM>) and store at least one instruction or a protocol or a parameter for the provided function, process, and/or method. The memory (<NUM>) may include read-only memory (ROM) and/or random access memory (RAM) and/or hard disk and/or CD-ROM and/or DVD and/or other storage devices.

<FIG> illustrates a base station according to embodiments of the present disclosure.

Referring to the <FIG>, the base station (<NUM>) may include a processor (<NUM>), a transceiver (<NUM>) and a memory (<NUM>). However, all of the illustrated components are not essential. The base station (<NUM>) may be implemented by more or less components than those illustrated in <FIG>. In addition, the processor (<NUM>) and the transceiver (<NUM>) and the memory (<NUM>) may be implemented as a single chip according to another embodiment.

The base station (<NUM>) may correspond to an MN or a SN according to embodiments of the present disclosure.

The processor (<NUM>) may include one or more processors or other processing devices that control the provided function, process, and/or method. An operation of the base station (<NUM>) may be implemented by the processor (<NUM>). The processor (<NUM>) may control a signal flow between each block to perform the provided function, process, and/or method according to the embodiments of the present disclosure.

The memory (<NUM>) may store the control information or the data included in a signal obtained by the base station (<NUM>). The memory (<NUM>) may be connected to the processor (<NUM>) and store at least one instruction or a protocol or a parameter for the provided function, process, and/or method. The memory (<NUM>) may include read-only memory (ROM) and/or random access memory (RAM) and/or hard disk and/or CD-ROM and/or DVD and/or other storage devices.

Claim 1:
A method performed by a user equipment, UE, (<NUM>) in a communication system, the method comprising:
receiving (S202), from a first base station (<NUM>) associated with a master cell group, MCG, a first message for configuring a second base station (<NUM>) associated with a secondary cell group, SCG;
receiving (S204, S206), from the second base station (<NUM>), a second message including conditional primary secondary cell, PSCell, change, CPC, configuration including at least one configuration for at least one candidate PSCell and at least one condition to trigger an execution of CPC for each of the at least one candidate PSCell;
storing (S208) the CPC configuration; and
in case that a third message for releasing the SCG of the second base station is received (S210) from the first base station (<NUM>), releasing (S212) the SCG of the second base station and the stored CPC configuration.