Patent Description:
The standardization organization Third Generation Partnership Project (3GPP) is currently in the process of specifying a new Radio Interface called <NUM> New Radio (<NUM> NR) as well as a Next Generation Packet Core Network (NG-CN or NGC). The <NUM> NR will have three main components: a <NUM> Access Network (<NUM>-AN), a <NUM> Core Network (5GC), and a User Equipment (UE). In order to facilitate the enablement of different data services and requirements, the elements of the 5GC, also called Network Functions, have been simplified with some of them being software based so that they could be adapted according to need.

3GPP Draft R2-<NUM> relates to remaining issues concerning conditional change.

The example embodiments disclosed herein are directed to solving the issues relating to one or more of the problems presented in the prior art, as well as providing additional features that will become readily apparent by reference to the following detailed description when taken in conjunction with the accompany drawings. In accordance with various embodiments, example systems, methods, devices and computer program products are disclosed herein. It is understood, however, that these embodiments are presented by way of example and are not limiting, and it will be apparent to those of ordinary skill in the art who read the present disclosure that various modifications to the disclosed embodiments can be made while remaining within the scope of the appended claims.

One aspect disclosed herein is directed to a method for mobility enhancements. The method includes receiving, by a wireless communication device, a first radio resource control (RRC) message (e.g., an RRCReconfiguration message) including at least one of a conditional handover (CHO) configuration and a conditional primary secondary cell addition or change (CPAC) configuration. In some embodiments, the CHO configuration includes a CHO configuration index, a CHO candidate cell configuration, and a CHO execution condition. In some embodiments, the CPAC configuration includes a CPAC configuration index, a CPAC candidate cell configuration, and a CPAC execution condition. In some embodiments, the method includes selecting, by the wireless communication device responsive to receiving the first RRC message and based on at least one of the CHO execution condition and the CPAC execution condition, a special cell (SpCell) of a wireless communication node to perform a random access procedure (RAP). In some embodiments, the method includes transmitting, by the wireless communication device to the wireless communication node, a second RRC message (e.g., an RRCReconfigurationComplete message) to inform the wireless communication node that the wireless communication device selected the SpCell to perform the RAP.

In some embodiments, the second RRC message includes an information element indicating a cell identification information for the selected SpCell. In some embodiments, the cell identification information includes at least one of an SpCell frequency and a physical cell identifier (PCI), a candidate cell identifier, and the CHO or CPAC configuration index.

In some embodiments, the method includes performing, by the wireless communication device toward a distributed unit (DU) of the wireless communication node, the RAP. In some embodiments, the RAP causes the DU to send an F1-C signaling to a central unit (CU) of the wireless communication device. In some embodiments, the F1-C signaling includes an indication of a cell identification information for the selected SpCell.

In some embodiments, the cell identification information corresponds to a cell global identity (CGI) or a cell radio network temporary identifier (C-RNTI).

In some embodiments, the method includes performing, by the wireless communication device toward a distributed unit (DU) of the wireless communication node, the RAP. In some embodiments, the RAP causes the DU to send an F1-U signaling to a central unit (CU) of the wireless communication device. In some embodiments, the F1-U signaling includes an indication of a cell identification information associated with the SpCell.

In some embodiments, the method includes receiving, by a wireless communication device from a first wireless communication node, a first radio resource control (RRC) message including a conditional primary secondary cell addition or change (CPAC) configuration. In some embodiments, the CPAC configuration includes a CPAC configuration index, a CPAC candidate cell configuration, and a CPAC execution condition. In some embodiments, the wireless communication device is not configured with a signaling radio bearer (SRB) type corresponding to SRB3. In some embodiments, the method includes selecting, by the wireless communication device and based on the CPAC execution condition, a primary secondary cell (PSCell) residing in a secondary wireless communication node to perform the CPAC. In some embodiments, the method includes transmitting, by the wireless communication device to the first wireless communication node, a second RRC message (e.g., an MN RRCReconfigurationComplete message) to inform the first wireless communication node that the wireless communication device selected the secondary wireless communication node to perform the CPAC.

In some embodiments, the second RRC message includes an information element indicating a cell identification information for the selected PSCell. In some embodiments, the cell identification information includes at least one of a primary secondary cell (PSCell) frequency and a physical cell identifier (PCI), a candidate cell identifier, and a CPAC configuration index.

In some embodiments, the second RRC message further causes the first wireless communication node to transmit a third RRC message (e.g., SN RRCReconfigurationComplete message) to the secondary wireless communication node based on the cell identification information for the selected PSCell. In some embodiments. In some embodiments, the third RRC message indicates that the wireless communication device has triggered the execution of CPAC.

In some embodiments, the method includes receiving, by a wireless communication device from a first wireless communication node, a radio resource control (RRC) message including a conditional primary secondary cell addition or change (CPAC) configuration. In some embodiments, the CPAC configuration includes a CPAC configuration index, a CPAC candidate cell configuration and a CPAC execution condition. In some embodiments, the wireless communication device is not configured with a signaling radio bearer (SRB) type corresponding to SRB3. In some embodiments, the method includes selecting, by the wireless communication device and based on the CPAC execution condition, a primary secondary cell (PSCell) residing in a secondary wireless communication node to perform the CPAC. In some embodiments, the method includes applying, by the wireless communication device, a CPAC candidate cell configuration for the selected PSCell. In some embodiments, the method includes determining, by the wireless communication device, a signaling radio bearer (SRB) type configured for the selected PSCell. In some embodiments, the method includes performing, by the wireless communication device, a random access procedure (RAP) at a PSCell.

In some embodiments, the SRB type configured for the selected PSCell corresponds to SRB3 and the method includes transmitting, by the wireless communication device to the secondary wireless communication node via SRB3, a second RRC message indicating that the wireless communication device has triggered the execution of CPAC.

In some embodiments, the method includes transmitting, by a wireless communication node to a wireless communication device, a first radio resource control (RRC) message including at least one of a conditional handover (CHO) configuration and a conditional primary secondary cell addition or change (CPAC) configuration. In some embodiments, the CHO configuration includes a CHO configuration index, a CHO candidate cell configuration, and a CHO execution condition. In some embodiments, the CPAC configuration includes a CPAC configuration index, a CPAC candidate cell configuration, and a CPAC execution condition. In some embodiments, the first RRC message causes the wireless communication device to: select, based on at least one of the CHO execution condition and the CPAC execution condition, a special cell (SpCell) of a wireless communication node to perform a random access procedure (RAP), and transmit a second RRC message to the wireless communication node. In some embodiments, the method includes receiving, by the wireless communication node from the wireless communication device, the second RRC message. In some embodiments, the method includes determining, by the wireless communication node, that the wireless communication device selected the SpCell to perform the RAP.

In some embodiments, the second RRC message includes an information element indicating a cell identification information for the selected SpCell, wherein the cell identification information includes at least one of an SpCell frequency and a physical cell identifier (PCI), a candidate cell identifier, and a CHO or CPAC configuration index.

In some embodiments, the first RRC message further causes the wireless communication device to: perform, toward a distributed unit (DU) of the wireless communication node, the RAP. In some embodiments, the RAP causes the DU to send an F1-C signaling to a central unit (CU) of the wireless communication device. In some embodiments, the F1-C signaling includes an indication of a cell identification information for the selected SpCell.

In some embodiments, the first RRC message causes the wireless communication device to: perform, toward a distributed unit (DU) of the wireless communication node, the RAP. In some embodiments, the RAP causes the DU to send an F1-U signaling to a central unit (CU) of the wireless communication device. In some embodiments, the F1-U signaling includes an indication of a cell identification information for the selected SpCell.

In some embodiments, the method includes transmitting, by a first wireless communication node to a wireless communication device, a first radio resource control (RRC) message including a conditional primary secondary cell addition or change (CPAC) configuration. In some embodiments, the CPAC configuration includes a CPAC configuration index, a CPAC candidate cell configuration and a CPAC execution condition. In some embodiments, the wireless communication device is not configured with a signaling radio bearer (SRB) type corresponding to SRB3. In some embodiments, the first RRC message causes the wireless communication device to: select, based on the CPAC execution condition, a primary secondary cell (PSCell) residing in a secondary wireless communication node to perform the CPAC, and transmit a second RRC message to the wireless communication node. In some embodiments, the method includes receiving, by the first wireless communication node from the wireless communication device, the second RRC message. In some embodiments, the method includes determining, by the first wireless communication node, that the wireless communication device selected the secondary wireless communication node to perform the CPAC.

In some embodiments, the second RRC message includes an information element indicating a cell identification information for the selected PSCell. In some embodiments, the cell identification information includes at least one of a primary secondary cell (PSCell) frequency and a physical cell identifier (PCI), a candidate cell identifier, and a candidate CPAC configuration index.

In some embodiments, the method includes transmitting, by the first wireless communication node and based on the cell identification information for the selected PSCell, a third RRC message (e.g., e.g., SN RRCReconfigurationComplete message) to the secondary wireless communication node, wherein the third RRC message indicates that the wireless communication device has triggered the execution of CPAC.

In some embodiments, the method includes transmitting, by a first wireless communication node to a wireless communication device, a radio resource control (RRC) message including a conditional primary secondary cell addition or change (CPAC) configuration. In some embodiments, the CPAC configuration includes a CPAC configuration index, a CPAC candidate cell configuration, and a CPAC execution condition. In some embodiments, the wireless communication device is not configured with a signaling radio bearer (SRB) type corresponding to SRB3. In some embodiments, the RRC message causes the wireless communication device to: select, based on the CPAC condition, a primary secondary cell (PSCell) residing in a secondary wireless communication node to perform the CPAC, apply a CPAC candidate cell configuration for the selected PSCell, determine a signaling radio bearer (SRB) type configured for the selected PSCell, and perform a random access procedure (RAP) at a PSCell.

In some embodiments, the SRB type configured for the selected PSCell corresponds to SRB3, wherein the RRC message further causes the wireless communication device to: transmit, to the secondary wireless communication node via SRB3, a second RRC message indicating that the wireless communication device has triggered the execution of CPAC, and the method includes receiving, by the secondary wireless communication node via the SRB3, the second RRC message.

The above and other aspects and their embodiments are described in greater detail in the drawings, the descriptions, and the claims.

The following acronyms are used throughout the present disclosure:.

Mobility performance is one of the most important performance metrics for long term evolution (LTE) and 5th Generation (<NUM>) new radio (NR). In addition to traditional voice and internet data service, lots of innovative services appear with various quality of service (QoS) requirements in recent years. For example, modern services such as remote control, aerial, industrial automation, industrial control, Augmented Reality (AR) and Virtual Reality (VR) require ultra-reliability and low latency. That is, the mobility performance for such services should be guaranteed with very high reliability (robust) and very low interruption time. For example, a latency target of the interruption time during handover should be as small as possible (e.g., close to <NUM> or <NUM>). Thus, a mechanism is needed for improving the mobility performance to meet the requirements for minimal interruption and high reliability.

Accordingly, the systems and methods discussed herein provide a mechanism for improving the mobility performance to meet the requirements for minimal interruption and high reliability.

That is, as discussed in greater detail below, the present disclosure enhances the conditional handover (CHO) procedure and the conditional primary secondary cell addition or change (CPAC) procedure by providing system and methods for: (<NUM>) indicating the selected SpCell to a target gNB-CU in case of a CU/DU split, (<NUM>) transferring the SN RRCReconfigurationComplete message to a target SN in the instance that multiple candidate SNs are configured, and (<NUM>) directly transferring the SN RRCReconfigurationComplete message to a target PSCell at the execution of CPAC.

<FIG> illustrates a block diagram of an example wireless communication system <NUM> for transmitting and receiving wireless communication signals (e.g., OFDM/OFDMA signals) in accordance with some embodiments of the present disclosure. The system <NUM> may include components and elements configured to support known or conventional operating features that need not be described in detail herein. In one illustrative embodiment, system <NUM> can be used to communicate (e.g., transmit and receive) data symbols in a wireless communication environment such as the wireless communication environment <NUM> of <FIG>, as described above.

To improve mobility reliability (e.g., mobility robust), a Conditional Handover (CHO) procedure is promoted. Conditional Handover is defined as having a configured CHO execution condition that determines when/whether the corresponding handover command is executed. Responsive to receiving the CHO configuration, UE starts to evaluate the condition and only executes the HO command once the condition is met.

<FIG> illustrates a flow diagram of an example CHO procedure, in accordance with some embodiments of the present disclosure. The example environment <NUM> includes a UE <NUM> (e.g., UE <NUM> in <FIG>), a source cell 302A (sometimes referred to as, "wireless communication node"), and/or a target cell 302B (sometimes referred to as, "wireless communication node"). In some embodiments, the source cell 302A may be a "first" wireless communication node having identical or similar functionality as the BS <NUM> in <FIG> and the target cell 302B may be a "second" wireless communication node having identical or similar functionality as the BS <NUM> in <FIG>.

At operation S110, the UE <NUM> may send (e.g., transmit, deliver, etc.) a message (labeled in <FIG> as, "S110 Measurement Report) to the source cell 302A to report the measurement result of the target cell 302B. At operation S120, the source cell 302A makes a decision on the usage of CHO to handoff the UE based on the Measurement Report information or RRM information. At operation S130, the source cell 302A sends a CHO request (labeled in <FIG> as, "S130. CHO request") to the target cell 302B. At operation S140, the target cell 302B sends a message (labeled in <FIG> as, "CHO request Acknowledge") to the source cell 302A. At operation S150, the source cell 302A sends a message (labeled in <FIG>. as, "RRCReconfiguration") to the UE <NUM>, where the message includes a CHO configuration. In some embodiments, the CHO configuration may include the configuration of the target cell 302B and/or the corresponding CHO execution condition of the target cell 302B.

At operation S160, the UE <NUM> sends a message (labeled in <FIG> as, "RRCReconfigurationComplete") to the source cell 302A. At operation S170, the UE <NUM> maintains a connection with the source cell 302A after receiving the CHO configuration, and starts to evaluate the CHO execution condition for the target cell 302B. At operation S180, if the CHO execution condition is fulfilled (e.g., satisfied, met, achieved, etc.), then the UE <NUM> performs a handover to the target cell 302B and applies the corresponding configuration received at operation S150. At operation S180, the UE <NUM> accesses the target cell 302B. At operation S190, the UE <NUM> sends a message (labeled in <FIG> as, "RRCReconfigurationComplete") to the target cell 302B.

The UE <NUM> in the wireless network can operate in Dual Connectivity, including intra-E-UTRA DC or Multi-Radio DC (MR-DC). In case of intra-E-UTRA DC, both the MN and SN may provide E-UTRA access. While in case of MR-DC, one node provides NR access and the other one provides either E-UTRA or NR access. One or multiple serving cells can be configured both on MN and SN. Serving cells configured on MN are defined as a Master Cell Group (MCG) while serving cells configured on SN are defined as a Secondary Cell Group (SCG). In each cell group, there's one primary cell and the others are secondary cell. The primary cell in the MCG is denoted as PCell while the primary cell in the SCG is denoted as PSCell. When operating in DC, a Radio Bearer (RB) can be configured to utilize either the MCG resources (MCG bearer) or SCG resources (MCG bearer) or both MCG and SCG resources (split bearer).

<FIG> illustrates a block diagram of an example <NUM> environment for a secondary node (SN) change, in accordance with some embodiments of the present disclosure. The example environment <NUM> includes a UE <NUM>, a master node 402A (shown in <FIG> as "MN"), a "first" secondary wireless communication node 402B (shown in <FIG> as "SN1"), and a "second" secondary wireless communication node 402C (shown in <FIG> as "SN2"). In some embodiments, any of the MN 402A, the SN 402B, and the SN 402C may be a BS <NUM> in <FIG>.

Cell 403A (shown in <FIG> as, "cell1"), Cell 403B (shown in <FIG> as, "cell2"), and Cell 403C (shown in <FIG> as, "cell3") are the corresponding cells generated by MN 402A, SN 402B and SN 402C respectively. X interfaces may be deployed between MN 402A and SN 402B, and SN 402C respectively. At time T1, the UE <NUM> is operating in DC between MN 402A and SN 402B. With the movement of the UE <NUM>, at time T2, the SN is changed from SN 402B to SN 402C. The SN change can be initiated either by the MN 402A or the source SN.

To improve mobility reliability (i.e., mobility robust) in case of SN change or SN addition, a Conditional PSCell Addition and PSCell Change (CPAC) may also be promoted. Similar to CHO, CPAC is defined as having a configured CPAC execution condition that determines when and/or whether the corresponding PSCell addition/change command is executed. Responsive to receiving the CPAC configuration, the UE <NUM>, in some embodiments, starts to evaluate the condition and only executes the CPAC command once the condition is met.

<FIG> illustrates a block diagram of an example environment of a 5GC system supporting a wireless communication node having a central unit (CU) / distributed unit (DU) split architecture, in accordance with some embodiments of the present disclosure. In case of CHO/CPAC, a target node can be a CU/DU split structure. The environment <NUM> includes a 5GC system <NUM> that is coupled to a gNB <NUM> (e.g., a target node). The gNB <NUM> includes of a gNB Central Unit (gNB-CU) <NUM> and one or more gNB Distributed Units (gNB-DU) 505A, 505B (collectively referred to as, "gNB-DU <NUM>"). The gNB-CU <NUM> and a gNB-DU <NUM> are connected via an F1 interface. The gNB-CU <NUM> may be defined as a logical node hosting RRC, SDAP and PDCP protocols of the gNB <NUM> or RRC and PDCP protocols of the en-gNB that controls the operation of one or more gNB-DUs <NUM>. The gNB-DU <NUM> may be defined as a logical node hosting RLC, MAC and PHY layers of the gNB <NUM> (sometimes referred to as, "en-gNB"), and its operation may be partly controlled by gNB-CU <NUM>. One gNB-DU <NUM> may support one or multiple cells. One cell may be supported by only one gNB-DU <NUM>.

In case of CHO/CPAC, multiple candidate SpCells (e.g., PCell and/or PSCell) can be resided in one target node. For example, multiple candidate SpCells may belong to one gNB-CU, but links (e.g., connect, associate, attach, etc.) to one or more gNB-DUs <NUM>. Responsive to triggering the execution of CHO/CPAC, the UE (e.g., UE <NUM> in <FIG>) may perform a random access procedure (RAP) to the selected (e.g., target cell) SpCell resided in the target gNB-DU <NUM> and/or send (e.g., transmit, deliver, etc.) the RRCReconfigurationComplete message to the target SpCell if there is a Signal Radio Bearer (SRB) located in the target node (e.g., SRB1, SRB3, etc.), as shown in operations S180 and S190 in <FIG>. The target gNB-DU <NUM> may send the UL RRC MESSAGE TRANSFER to transfer the RRCReconfigurationComplete message (if any) to the gNB-CU <NUM> over the F1 interface.

However, in some embodiments, no SpCell index is included in the existing UL RRC MESSAGE TRANSFER or RRCReconfigurationComplete message. As such, the target gNB-CU <NUM> may have no idea as to which candidate SpCell is selected by the UE.

In order to inform the target gNB-CU about the selected SpCell, there are several alternatives that may be considered as follows:.

The UE may send an RRC complete message including the indication of selected cell identification information (e.g., target SpCell frequency and PCI; candidate cell ID; candidate CHO/CPAC configuration index) to the BS. For example, the RRC complete message may include the indication as one information element in the RRCReconfigurationComplete message.

In some embodiments (sometimes referred to as, "Embodiment 1a"), responsive to triggering the execution of CHO, the UE may send an RRCReconfigurationComplete message including the indication of the selected PCell information (e.g., target PCell frequency + PCI; candidate cell ID; candidate CHO configuration index) to the target gNB-DU. The target gNB-DU may send an UL RRC MESSAGE TRANSFER message to the target gNB-CU to convey the received RRCReconfigurationComplete message.

In some embodiments (sometimes referred to as, "Embodiment 1b"), responsive to triggering the execution of CPAC, the UE may send an RRCReconfigurationComplete message including the indication of the selected PSCell information (e.g., target PSCell frequency + PCI; candidate cell ID; candidate CPAC configuration index) to the target SN gNB-DU. The target SN gNB-DU may send a UL RRC MESSAGE TRANSFER message to the target SN gNB-CU to convey the received RRCReconfigurationComplete message.

In some embodiments (sometimes referred to as, "Embodiment 1c"), responsive to triggering the execution of CPAC, the UE may send a MN RRC complete message (e.g., RRCReconfigurationComplete/RRCConnectionReconfigurationComplete, or ULInformationTransferMRDC) including an embedded SN RRCReconfigurationComplete message to the MN. The indication of the selected PSCell information (e.g. target PSCell frequency + target PSCell PCI; candidate cell ID; candidate CPAC configuration index) may be included in the SN RRCReconfigurationComplete message. The MN may send the SN RRCReconfigurationComplete message to the target SN gNB-CU via X2/Xn signaling.

Responsive to performing (e.g., executing, implementing, conducing, etc.) a Random Access Procedure (RAP) at the target gNB-DU, the target gNB-DU may send a F1-C signaling including the indication of selected cell identification information (e.g., target SpCell frequency + PCI; candidate cell ID; candidate CHO configuration index; CGI; C-RNTI) to the target gNB-CU, i.e. include the indication as one information element in the UL RRC MESSAGE TRANSFER message.

In some embodiments (sometimes referred to as, "Embodiment 2a"), responsive to triggering the execution of CHO, the UE may send an RRCReconfigurationComplete message to the target gNB-DU. The target gNB-DU may send an UL RRC MESSAGE TRANSFER message including the indication of selected PCell information (e.g., target PCell frequency + PCI; candidate cell ID; candidate CHO configuration index; CGI; C-RNTI) to the target gNB-CU to convey the received RRCReconfigurationComplete message.

In some embodiments (sometimes referred to as, "Embodiment 2b"), responsive triggering the execution of CPAC, the UE may send an RRCReconfigurationComplete message to the target SN gNB-DU. The target SN gNB-DU may send an UL RRC MESSAGE TRANSFER message including the indication of selected PSCell information (e.g., target PSCell frequency + PCI; candidate cell ID; candidate CHO configuration index; CGI; C-RNTI) to the target SgNB-CU to convey the received RRCReconfigurationComplete message.

Responsive to performing a RAP at the target gNB-DU, the target gNB-DU may send a F1-U signaling including the indication of selected cell identification information (e.g., target SpCell frequency + PCI; candidate cell ID; candidate CHO configuration index; CGI; C-RNTI) to the target gNB-CU via F1-U signaling. For example the F1-U signaling may include the indication as one information element in the DL DATA DELIVERY STATUS (DDDS) message.

In some embodiments (sometimes referred to as, "Embodiment 3a"), responsive to triggering the execution of CHO, the UE may perform a RAP towards the target gNB-DU. A RAP may be performed at the target gNB-DU. The target gNB-DU may send a DDDS frame including the indication of selected PCell information (e.g., target PCell frequency + PCI; candidate cell ID; candidate CHO configuration index; CGI; C-RNTI) to inform the target gNB-CU.

In some embodiments (sometimes referred to as, "Embodiment 3b"), responsive to triggering the execution of CPAC, the UE may perform a RAP towards the target SN gNB-DU. A RAP may be performed at the target SN gNB-DU. The target SN gNB-DU may send a DDDS frame including the indication of selected PSCell information (e.g., target PCell frequency + PCI; candidate cell ID; candidate CHO configuration index; CGI; C-RNTI) to inform the target SN gNB-CU.

The target gNB-CU and gNB-DU may allocate (e.g., assign, distribute, etc.) an individual transport network layer (TNL) address information for F1-U interface of each candidate SpCell in the handover preparation phase.

In some embodiments (sometimes referred to as, "Embodiment 4a"), responsive to receiving the CHO request from the source node, the target gNB-CU and/or gNB-DU may allocate an individual TNL address information for F1-U interface of each candidate PCell. A RAP may be performed at the target gNB-DU. The target gNB-DU may send a DDDS frame to inform the target gNB-CU. The target gNB-CU can infer the selected PCell from the TNL address of DDDS.

In some embodiments (sometimes referred to as, "Embodiment 4b"), responsive to receiving the CPAC request from the source SN, the target SN gNB-CU and/or gNB-DU may allocate an individual TNL address information for F1-U interface of each candidate PSCell. A RAP may be performed at the target SN gNB-DU. The target SN gNB-DU may send a DDDS frame to inform the target SN gNB-CU. The target SN gNB-CU can infer the selected PSCell from the TNL address of DDDS.

<FIG> is a flow diagram depicting a method for improving mobility performance, in accordance with some embodiments of the present disclosure. Additional, fewer, or different operations may be performed in the method depending on the particular embodiment. In some embodiments, some or all operations of method <NUM> may be performed by a wireless communication node, such as BS <NUM> in <FIG>. In some operations, some or all operations of method <NUM> may be performed by a wireless communication device, such as UE <NUM> in <FIG>. Each operation may be re-ordered, added, removed, or repeated.

As shown, the method <NUM> includes, in some embodiments, the operation <NUM> of receiving, by a wireless communication device, first radio resource control (RRC) message including at least one of a conditional handover (CHO) configuration and a conditional primary secondary cell addition or change (CPAC) configuration, wherein the CHO configuration includes a CHO configuration index, a CHO candidate cell configuration, and a CHO execution condition, wherein the CPAC configuration includes a CPAC configuration index, a CPAC candidate cell configuration, and a CPAC execution condition. The method includes, in some embodiments, the operation <NUM> of selecting, by the wireless communication device responsive to receiving the first RRC message and based on at least the CHO execution condition and the CPAC execution condition, a special cell (SpCell) of a wireless communication node to perform a random access procedure (RAP). The method includes, in some embodiments, the operation <NUM> of transmitting, by the wireless communication device to the wireless communication node, a second RRC message to inform the wireless communication node that the wireless communication device selected the SpCell to perform the RAP.

As shown, the method <NUM> includes, in some embodiments, the operation <NUM> of receiving, by a wireless communication device from a first wireless communication node, a first radio resource control (RRC) message including a conditional primary secondary cell addition or change (CPAC) configuration, wherein the CPAC configuration includes a CPAC configuration index, a CPAC candidate cell configuration, and a CPAC execution condition, wherein the wireless communication device is not configured with a signaling radio bearer (SRB) type corresponding to SRB3. The method includes, in some embodiments, the operation <NUM> of selecting, by the wireless communication device and based on the CPAC execution condition, a primary secondary cell (PSCell) residing in a secondary wireless communication node to perform the CPAC. The method includes, in some embodiments, the operation <NUM> of transmitting, by the wireless communication device to the first wireless communication node, a second RRC message to inform the first wireless communication node that the wireless communication device selected the secondary wireless communication node to perform the CPAC.

As shown, the method <NUM> includes, in some embodiments, the operation <NUM> of receiving, by a wireless communication device from a first wireless communication node, a radio resource control (RRC) message including a conditional primary secondary cell addition or change (CPAC) configuration, wherein the CPAC configuration includes a CPAC configuration index, a CPAC candidate cell configuration and a CPAC execution condition, wherein the wireless communication device is not configured with a signaling radio bearer (SRB) type corresponding to SRB3. The method includes, in some embodiments, the operation <NUM> of selecting, by the wireless communication device and based on the CPAC execution condition, a primary secondary cell (PSCell) residing in a secondary wireless communication node to perform the CPAC. The method includes, in some embodiments, the operation <NUM> of applying, by the wireless communication device, a CPAC candidate cell configuration for the selected PSCell. The method includes, in some embodiments, the operation <NUM> of determining, by the wireless communication device, a signaling radio bearer (SRB) type configured for the selected PSCell. The method includes, in some embodiments, the operation <NUM> of performing, by the wireless communication device, a random access procedure (RAP) at a PSCell.

In case of CPAC, the UE may send a MN RRC complete message (e.g., RRCReconfigurationComplete/RRCConnectionReconfigurationComplete, or ULInformationTransferMRDC) including an embedded SN RRC complete message (e.g., RRCReconfigurationComplete) to the MN at configuration of CPAC and execution of CPAC when no SRB3 is configured. Responsive to receiving the MN RRC complete message, the MN may inform the target SN.

However, if multiple candidate SNs are configured for CPAC, then the MN may have no idea as to which candidate SN should be informed.

In order to inform the MN about the selected candidate SN, the UE sends a MN RRC complete message (e.g., RRCReconfigurationComplete/RRCConnectionReconfigurationComplete, or ULInformationTransferMRDC) including the indication of the selected cell information (e.g., target PSCell frequency + PCI; candidate cell ID; candidate CHO/CPAC configuration index) to the MN. For example, the MN RRC complete message may include the indication as one information element in the RRC complete message. The MN may send the SN RRCReconfigurationComplete message to the corresponding SN according to the indicated cell information.

The MN may send an RRCReconfiguration message with CPAC configuration to the UE. The CPAC configuration may include the configuration of the target PSCell and/or the corresponding CPAC execution condition of the target PSCell.

Responsive to receiving the RRCReconfiguration message, the UE sends a MN RRC complete message (e.g., RRCReconfigurationComplete / RRCConnectionReconfigurationComplete, or ULInformationTransferMRDC) including one or more embedded SN RRCReconfigurationComplete messages to the MN. That is, each embedded SN RRCReconfigurationComplete may be linked with an indication of the cell information (e.g., target PSCell frequency + PCI; candidate cell ID; candidate CHO/CPAC configuration index).

The MN may transfer the SN RRCReconfigurationComplete message to the corresponding SN according to the indicated cell information.

Responsive to triggering the execution of CPAC (i.e., the corresponding execution condition is met), the UE may send a MN RRC complete message (e.g., RRCReconfigurationComplete / RRCConnectionReconfigurationComplete, or ULInformationTransferMRDC) including an embedded SN RRCReconfigurationComplete message to the MN, which also may include the indication of the selected cell information (e.g., target PSCell frequency + PCI; candidate cell ID; candidate CHO/CPAC configuration index).

As shown, the method <NUM> includes, in some embodiments, the operation <NUM> of transmitting, by a wireless communication node to a wireless communication device, a first radio resource control (RRC) message including at least one of a conditional handover (CHO) configuration and a conditional primary secondary cell addition or change (CPAC) configuration, wherein the CHO configuration includes a CHO configuration index, a CHO candidate cell configuration , and a CHO execution condition , wherein the CPAC configuration includes a CPAC configuration index, a CPAC candidate cell configuration, and a CPAC execution condition, wherein the first RRC message causes the wireless communication device to: select, based on at least one of the CHO execution condition and the CPAC execution condition, a special cell (SpCell) of a wireless communication node to perform a random access procedure (RAP), and transmit a second RRC message to the wireless communication node. The method includes, in some embodiments, the operation <NUM> of receiving, by the wireless communication node from the wireless communication device, the second RRC message. The method includes, in some embodiments, the operation <NUM> of determining, by the wireless communication node, that the wireless communication device selected the SpCell to perform the RAP.

As shown, the method <NUM> includes, in some embodiments, the operation <NUM> of transmitting, by a first wireless communication node to a wireless communication device, a first radio resource control (RRC) message including a conditional primary secondary cell addition or change (CPAC) configuration, wherein the CPAC configuration includes a CPAC configuration index, a CPAC candidate cell configuration and a CPAC execution condition, wherein the wireless communication device is not configured with a signaling radio bearer (SRB) type corresponding to SRB3, wherein the first RRC message causes the wireless communication device to: select, based on the CPAC execution condition, a primary secondary cell (PSCell) residing in a secondary wireless communication node to perform the CPAC, and transmit a second RRC message to the wireless communication node. The method includes, in some embodiments, the operation <NUM> of receiving, by the first wireless communication node from the wireless communication device, the second RRC message. The method includes, in some embodiments, the operation <NUM> of determining, by the first wireless communication node, that the wireless communication device selected the secondary wireless communication node to perform the CPAC.

When no SRB3 is configured, the SN RRCReconfiguration message may be embedded in the MN RRCReconfiguration/RRCConnectionReconfiguration message to transfer to the UE. At the execution of CPAC, the UE may apply the new configuration for the target PSCell, perform RAP to the target PSCell, and/or send the RRCReconfigurationComplete message to the target PSCell via SRB3 if the SRB3 is configured for the target PSCell.

The MN may send an RRCReconfiguration message with CPAC configuration to the UE. The CPAC configuration may include the configuration of the target cell and/or the corresponding CPAC execution condition of the target cell.

Responsive to receiving the RRCReconfiguration message, the UE sends a MN RRC complete message (e.g., RRCReconfigurationComplete / RRCConnectionReconfigurationComplete, or ULInformationTransferMRDC) including an embedded SN RRCReconfigurationComplete messages to the MN.

The UE may start to evaluate the CPAC execution condition for the target PSCell. If the CPAC execution condition is fulfilled, then the UE may apply the corresponding CPAC configuration and/or perform a RAP towards the target PSCell.

The UE may send an RRCReconfigurationComplete message to the target PSCell via SRB3 if SRB3 is configured.

A person of ordinary skill in the art would further appreciate that any of the various illustrative logical blocks, modules, processors, means, circuits, methods and functions described in connection with the aspects disclosed herein can be implemented by electronic hardware (e.g., a digital implementation, an analog implementation, or a combination of the two), firmware, various forms of program (e.g., a computer program product) or design code incorporating instructions (which can be referred to herein, for convenience, as "software" or a "software module), or any combination of these techniques.

Claim 1:
A method comprising:
receiving, by a wireless communication device (<NUM>), a first radio resource control, RRC, message including a conditional handover, CHO, configuration, wherein the CHO configuration includes a CHO configuration index, a CHO candidate cell configuration, and a CHO execution condition;
selecting, by the wireless communication device (<NUM>) responsive to receiving the first RRC message and based on the CHO execution condition, a special cell, SpCell, (<NUM>) of a wireless communication node (<NUM>) to perform a random access procedure, RAP; and
transmitting, by the wireless communication device (<NUM>) to the wireless communication node (<NUM>), a second RRC message to inform the wireless communication node that the wireless communication device selected the SPCell to perform the RAP.