WO2021240052A1

WO2021240052A1 - Dual active protocol stack (daps) mobility enhancements for dual connectivity scenarios

Info

Publication number: WO2021240052A1
Application number: PCT/FI2021/050328
Authority: WO
Inventors: Srinivasan Selvaganapathy; Krzysztof Kordybach; Amaanat ALI
Original assignee: Nokia Technologies Oy
Priority date: 2020-05-28
Filing date: 2021-05-04
Publication date: 2021-12-02
Also published as: EP4158942A1; EP4158942A4

Abstract

Systems, methods, apparatuses, and computer program products for dual active protocol stack (DAPS) mobility enhancements for dual connectivity scenarios. For example, certain embodiments may relate to a handover from a source master node to a target master node in dual connectivity, where a user equipment has a connection with 5 a source master radio link and a source secondary radio link. The user equipment (UE) and/or the master node (MN) may suspend the connection with the source MN. The source MN may transmit, and the UE may receive, a message to trigger radio link measurements with the source secondary radio link during the suspension. The UE may activate DAPS operation for simultaneous data transmission at the UE to a source 10 secondary radio link and a target master radio link and/or a target secondary radio link.

Description

TITLE: DUAL ACTIVE PROTOCOL STACK (DAPS) MOBILITY

ENHANCEMENTS FOR DUAL CONNECTIVITY SCENARIOS CROSS-REFERENCE TO RELATED APPLICATION:

This application claims priority to Indian Provisional Application No. 202041022373 filed May 28, 2020, which is incorporated herein by reference in its entirety.

FIELD: Some example embodiments may generally relate to mobile or wireless telecommunication systems, such as Long Term Evolution (LTE) or fifth generation (5G) radio access technology or new radio (NR) access technology, or other communications systems. For example, certain embodiments may relate to systems and/or methods for dual active protocol stack (DAPS) mobility enhancements for dual connectivity scenarios.

BACKGROUND:

Examples of mobile or wireless telecommunication systems may include the Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access Network (UTRAN), Long Term Evolution (LTE) Evolved UTRAN (E-UTRAN), LTE- Advanced (LTE-A), MulteFire, LTE-A Pro, and/or fifth generation (5G) radio access technology or new radio (NR) access technology. 5G wireless systems refer to the next generation (NG) of radio systems and network architecture. 5G is mostly built on a new radio (NR), but a 5G (or NG) network can also build on E-UTRA radio. It is estimated that NR may provide bitrates on the order of 10-20 Gbit/s or higher, and may support at least enhanced mobile broadband (eMBB) and ultra-reliable low-latency- communication (URLLC) as well as massive machine type communication (mMTC). NR is expected to deliver extreme broadband and ultra-robust, low latency connectivity and massive networking to support the Internet of Things (IoT). With IoT and maehine- to-machine (M2M) communication becoming more widespread, there will be a growing need for networks that meet the needs of lower power, low data rate, and long battery life. It is noted that, in 5G, the nodes that can provide radio access functionality to a user equipment (i.e., similar to Node B in UTRAN or eNB in LTE) may be named gNB when built on NR radio and may be named NG-eNB when built on E-UTRA radio.

SUMMARY:

According to a first embodiment, a method may be for a handover from a source master node to a target master node in dual connectivity. A user equipment (UE) may have a connection with a master radio link to the source master node and a secondary radio link to a source secondary node. The method may include receiving, by the UE from the source master node, a message associated with triggering radio link measurements with the secondary radio link during a suspension of the connection with the source master node. The method may include suspending the connection between the UE and the source master node. The method may include activating dual active protocol stack operation for data transmission at the UE with the secondary radio link and a target radio link to the target master node.

In a variant, the message may include radio resource control (RRC) configuration signaling. In a variant, the message may include one or more parameters related to at least one of a source radio condition threshold, of the master radio link, for starting the handover, use of a radio condition difference to adjust secondary radio link monitoring (RLM), or a timer to complete the dual active protocol stack operation for a secondary cell group (SCG).

In a variant, the method may further include receiving, from the target master node, a message associated with releasing the source master node. In a variant, the method may further include deactivating the dual active protocol stack operation based on the message associated with releasing the serving master node. In a variant, the message associated with releasing the source master node may include RRC reconfiguration signaling. In a variant, the method may include performing, based on activating the dual active protocol stack operation, a packet data convergence protocol (PDCP)-dual active protocol stack uplink transmission to the target master node on a first uplink grant. In a variant, the method may include performing, based on activating the dual active protocol stack operation, a random access channel (RACH) procedure. In a variant, the method may include completing the handover based on performing the RACH procedure.

In a variant, the method may further include checking a status of the master radio link relative to a threshold based on receiving the message. In a variant, the suspending or the activating may be based on the status of the master radio link satisfying the threshold. In a variant, the method may further include adjusting the radio link measurements for the secondary radio link based on a source radio condition offset indicated in the message. In a variant, the method may include, based on expiration of a timer, terminating the handover, or resuming master cell group (MCG) monitoring.

According to a second embodiment, a method may be for a handover from a source master node to a target master node in dual connectivity. A UE may have a connection with a master radio link to the source master node and a secondary radio link to a source secondary node. The method may include transmitting, by the source master node to the UE, a message. The message may be associated with triggering radio link measurements with the secondary radio link during a suspension of the connection with the source master node. The method may include suspending the connection between the UE and the source master node.

In a variant, the message may include RRC configuration signaling. In a variant, the message may include one or more parameters related to at least one of a source radio condition threshold, of the master radio link, for starting the handover, use of a radio condition difference to adjust secondary RLM, or a timer to complete the dual active protocol stack operation for a SCG. In a variant, operations of the source master node associated with a dual active protocol stack may be distributed between the source master node and the source secondary node. In a variant, the method may further include transmitting, to the source secondary node, an indication that the UE is to activate a dual active protocol stack operation. In a variant, the indication may be associated with causing the source secondary node to start forwarding one or more packets to the target master node and to continue scheduling via the source master node while suspending a transmission via the source secondary node.

In a variant, the method may further include transmitting, to the UE, an indication associated with causing the DAPS operation to be activated. In a variant, the method may further include transmitting, to the UE, another indication associated with causing the DAPS operation to be deactivated.

According to a third embodiment, a method may be for a handover from a source secondary node to a target secondary node in dual connectivity. A UE may have a connection with a master radio link to a source master node and a secondary radio link to the source secondary node. The method may include receiving, by the UE from the source master node, a message that indicates that the handover is to be performed. The method may include suspending the connection between the UE and the source master node. The method may include activating dual active protocol stack operation for data transmission at the UE with the secondary radio link and a target radio link to the target secondary node.

In a variant, the message may include RRC configuration signaling. In a variant, the message may include one or more parameters related to at least one of a source radio condition threshold, of the master radio link, for starting the handover, use of a radio condition difference to adjust secondary RLM, or a timer to complete the dual active protocol stack operation for a SCG. In a variant, the method may further include receiving, from the target secondary node, a message associated with releasing the source secondary node. In a variant, the method may further include deactivating the dual active protocol stack operation based on the message associated with releasing the source secondary node. In a variant, the message associated with releasing the source secondary node may include RRC reconfiguration signaling. In a variant, the suspending or the activating may be based on a status of the master radio link satisfying the threshold. In a variant, the method may include, based on expiration of a timer, terminating the handover, or resuming MCG monitoring. A fourth embodiment may be directed to an apparatus including at least one processor and at least one memory comprising computer program code. The at least one memory and computer program code may be configured, with the at least one processor, to cause the apparatus at least to perform the method according to the first embodiment, the second embodiment, or the third embodiment, or any of the variants discussed above.

A fifth embodiment may be directed to an apparatus that may include circuitry configured to perform the method according to the first embodiment, the second embodiment, or the third embodiment, or any of the variants discussed above. A sixth embodiment may be directed to an apparatus that may include means for performing the method according to the first embodiment, the second embodiment, or the third embodiment, or any of the variants discussed above.

A seventh embodiment may be directed to a computer readable medium comprising program instructions stored thereon for performing at least the method according to the first embodiment, the second embodiment, or the third embodiment, or any of the variants discussed above. An eighth embodiment may be directed to a computer program product encoding instructions for performing at least the method according to the first embodiment, the second embodiment, or the third embodiment, or any of the variants discussed above. BRIEF DESCRIPTION OF THE DRAWINGS :

For proper understanding of example embodiments, reference should be made to the accompanying drawings, wherein:

Fig. 1 illustrates an example signal diagram of a reference message sequence for primary secondary cell (PSCell) change; Fig. 2 illustrates an example of a packet data convergence protocol (PDCP) state transition during DAPS handover for a single connectivity handover;

Fig. 3 illustrates an example signal diagram of a handover of a UE with dual connectivity to a target cell with single connectivity;

Fig. 4 illustrates an example signal diagram of a master node (MN)-initiated secondary node (SN) change, according to some embodiments;

Fig. 5 illustrates an example signal diagram of DAPS handover, of a UE having dual connectivity at a source MN and a SN, to a target MN, according to some embodiments; Fig. 6 illustrates an example of a PDCP state transition for MN/SN-initiated primary secondary cell (PSCell) change with DAPS, according to some embodiments; Fig. 7 illustrates an example of a PDCP state transition handover from a MN to a gNB/eNB with DAPS configured for secondary cell group (SCG) bearers, according to some embodiments;

Fig. 8 illustrates an example of UE DAPS operations over a secondary radio link, according to some embodiments; Fig. 9 illustrates an example flow diagram of a method, according to some embodiments;

Fig. 10 illustrates an example flow diagram of a method, according to some embodiments;

Fig. 11a illustrates an example block diagram of an apparatus, according to an embodiment; and Fig. l ib illustrates an example block diagram of an apparatus, according to another embodiment.

DETAILED DESCRIPTION:

It will be readily understood that the components of certain example embodiments, as generally described and illustrated in the figures herein, may be arranged and designed in a wide variety of different configurations. Thus, the following detailed description of some example embodiments of systems, methods, apparatuses, and computer program products for DAPS mobility enhancements for dual connectivity scenarios is not intended to limit the scope of certain embodiments but is representative of selected example embodiments.

The features, structures, or characteristics of example embodiments described throughout this specification may be combined in any suitable manner in one or more example embodiments. For example, the usage of the phrases “certain embodiments,” “some embodiments,” or other similar language, throughout this specification refers to the fact that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment. Thus, appearances of the phrases “in certain embodiments,” “in some embodiments,” “in other embodiments,” or other similar language, throughout this specification do not necessarily all refer to the same group of embodiments, and the described features, structures, or characteristics may be combined in any suitable manner in one or more example embodiments. In addition, the phrase “set of’ refers to a set that includes one or more of the referenced set members. As such, the phrases “set of,” “one or more of,” and “at least one of,” or equivalent phrases, may be used interchangeably. Further, “or” is intended to mean “and/or,” unless explicitly stated otherwise.

Additionally, if desired, the different functions or operations discussed below may be performed in a different order and/or concurrently with each other. Furthermore, if desired, one or more of the described functions or operations may be optional or may be combined. As such, the following description should be considered as merely illustrative of the principles and teachings of certain example embodiments, and not in limitation thereof.

Dual active protocol stack (DAPS) handover was introduced in 3GPP release- 16 as part of mobility enhancements for NR/LTE. With DAPS handover, the user plane (UP) interruption time during handover may be reduced to 0 milliseconds (ms) or near 0 ms. The reduction in UP interruption time may be achieved by configuring a UE with simultaneous transmission/reception with a source node and target node during the handover execution window and with dual active protocol stack operation at higher layers. When the UE operates with dual connectivity at the time of handover at a source master node (MN), the DAPS handover towards a target master node with or without dual connectivity is not possible without increasing the UE capability for simultaneous operation over more than two radio links (simultaneously between source and target master node and secondary node (SN)).

Fig. 1 illustrates an example signal diagram of a reference message sequence for PSCell change. Fig. 1 illustrates a UE, a MN, a source SN (S-SN), a target SN (T-SN), a serving gateway (S-GW), and a mobility management entity (MME). As illustrated at 100, a MN may transmit, to a T-SN, a secondary gNB (SgNB) addition request. As illustrated at 102, the T-SN may transmit, and the MN may receive, a SgNB addition request acknowledge. The MN may transmit, to the S-SN, a SgNB release request at 104a, and the S-SN may transmit, to the MN, a SgNB release request acknowledge at 104b. At 106, the MN may transmit, to the UE, a radio resource configuration (RRC) connection reconfiguration message, and the UE may transmit, to the MN, a RRC connection reconfiguration complete message at 108.

As illustrated at 110, the MN may transmit, to the T-SN, a SgNB reconfiguration complete message. As illustrated at 112, the UE and the T-SN may perform a random access procedure. At 114a the S-SN may transmit, to the MN, a SN status transfer, and the MN may transmit the SN status transfer to the T-SN at 114b. Data forwarding of S- SN data may be performed from the MN to the T-SN at 116. At 118, the S-SN may transmit a secondary radio access technology (RAT) data volume report to the MN.

At 120, the MN may transmit an evolved universal terrestrial radio access (E-UTRA) radio access bearer (E-RAB) modification indication to the MME. As illustrated at 122, the S-GW and MME may perform operations related to bearer modification. As illustrated at 124, the S-GW may transmit an end marker packet to the MN, which may transmit the end marker packet to the T-SN. As illustrated at 126, the S-GW may send new path information to the T-SN. As illustrated at 128, the MME may transmit, to the MN, an E-RAB modification confirmation. As illustrated at 130, the MN may transmit, to the S-SN, an UE context release.

Fig. 2 illustrates an example of a PDCP state transition during DAPS handover for a single connectivity handover. As illustrated at 200, a UE may switch from normal PDCP (NR PDCP) operations to NR PDCP with DAPS operations based on reception of a handover command. As illustrated at 210, the UE may switch from the NR PDCP with DAPS operations to normal PDCP operations based on receiving a source protocol stack (PS) release.

Fig. 3 illustrates an example signal diagram of a handover of a UE with dual connectivity to a target cell with single connectivity. As part of a release, the release- 16 DAPS handover procedure proposed to release the secondary radio link during the DAPS handover. According to this procedure, if the UE had SCG bearers at the time of the DAPS handover, these bearers would experience an interruption similar to legacy handover scenarios during the handover as these bearers need to be mapped to the target eNB (T-eNB). For evolved universal terrestrial radio access (E-UTRA) NR dual connectivity (EN-DC) deployments, most of the bearers may be expected to be configured as SCG bearers for better offloading of traffic. In such cases, if the DAPS handover does not provide reduction of interruption time for these bearers, the benefits of using DAPS handover may be limited. Fig. 3 illustrates a UE, a S-MN, a S-SN, a target eNB (T-eNB), a S-GW, and a MME. As illustrated at 300, the S-MN may transmit, to the T-eNB, a handover request, and the T-eNB may transmit a handover request acknowledge to the S-MN at 302. At 304a, the S-MN may transmit, to the S-SN, a SgNB release request, and the S-SN may transmit, to the S-MN, a SgNB release request acknowledge at 304b. An RRC connection reconfiguration may be transmitted from the S-MN to the UE at 306. At 308, the UE and the T-eNB may perform operations for a random access procedure. At 312a and 312b, the S-SN may transmit a SN status transfer to the S-MN, and the S-MN may transmit the SN status transfer to the T-eNB.

At 314, data forwarding may be performed from the S-SN to the S-MN and from the S- MN to the T-eNB. At 316a, the S-SN may transmit a secondary RAT data volume report to the S-MN, and at 316b, the S-MN may transmit the secondary RAT report to the MME. At 318, the T-eNB may transmit a path switch request to the MME. At 320, the S-GW and the MME may perform operations related to bearer modification. At 322, the S-GW may transmit an end marker packet to the S-MN, and the S-MN may transmit the end marker packet to the T-eNB. At 324, the S-GW may transmit new path information to the T-eNB. A path switch request acknowledge may be transmitted from the MME to the T-eNB at 326. The T-eNB may transmit, at 328, a UE context release from the T-eNB to the S-MN and the S-MN may transmit, at 330, the UE context release to the S-SN.

Some embodiments described herein may provide for DAPS mobility enhancements for dual connectivity scenarios. For example, certain embodiments may relate to a handover from a source master node to a target master node in dual connectivity, where a user equipment has a connection with a source master radio link (e.g., between the UE and the source MN) and a source secondary radio link (e.g., between the UE and a source SN). The UE and/or the MN may suspend the connection with the source MN. The source MN may transmit, and the UE may receive, a message (e.g., a RRC configuration message) to trigger radio link measurements with the source secondary radio link during the suspension. The UE may activate DAPS operation for simultaneous data transmission at the UE to a source secondary radio link and a target master radio link (e.g., between the UE and a target MN) and/or a target secondary radio link (e.g., between the UE and a target SN).

In addition, as described elsewhere herein, the message may include various parameters, such as a parameter that indicates a source radio condition threshold for starting the handover, a parameter that indicates that a radio condition difference is to be used to adjust radio link monitoring (RLM) on the secondary radio link, and/or a parameter that indicates a time for completing SCG DAPS, in certain embodiments. In some embodiments, the DAPS operation of a source PS may be distributed between a MN and a SN for bearer operation that was anchored as secondary node. Further, in certain embodiments, the target MN, on reception of a DAPS indication from the source MN, may start forwarding packets to the target MN and/or may continue to schedule via the source MN while suspending the transmission via the source SN. In this way, certain embodiments described herein may provide for enhancements to enable the DAPS- based mobility for a MN-maintained PSCell change scenario and/or for handover from a MN with dual connectivity to a target node with single connectivity.

Certain embodiments described herein may provide for a source MN temporarily suspending a connection with the UE during the SN DAPS operation. In these cases, certain embodiments may provide for configuration of DAPS-based mobility for PSCell change via operations of an MN-initiated SN change. For example, certain embodiments for preparing a target SN for DAPS mobility may include a MN including an additional parameter in a SN addition request to indicate the DAPS activation needed for the PSCell change to the target SN. The target SN may prepare a RRC reconfiguration, with DAPS enabled for selected SN terminated bearers, and may include the RRC reconfiguration in a SN addition response message. The SN may include an additional parameter indicating that DAPS mobility is configured for at least one of the secondary cell group (SCG) bearers. This parameter may be used to enable additional configuration at the master cell group (MCG) side to enable DAPS operation for SCG. In addition, certain embodiments for RRC reconfiguration changes and UE behavior to activate DAPS for SCG may include the MN providing, in the RRC connection reconfiguration message, an additional parameter that identifies a serving cell threshold that may have to be satisfied for activation of DAPS for SCG (e.g., on secondary radio links). The MN may include an additional parameter that identifies a PSCell radio condition and/or timer values to disable source SCG operation and/or to switch to MN monitoring during the DAPS handover window. The MN may configure the UE operations on secondary radio link failure (S-RLF) as part of this reconfiguration message, such as whether the UE may declare complete RLF, disable DAPS for SCG, and/or switch to MN radio link monitoring, in certain embodiments.

In some embodiments, the MN and/or UE may suspend MCG operation, including radio link monitoring, to enable DAPS for SCG. The DAPS for SCG may include additional criteria associated with facilitating a minimization of the impact of suspending MN radio link monitoring by using a fall-back mechanism to disable DAPS operation based on specific radio conditions. During the time the MN remains suspended, the UE may be able to use uplink transmit (Tx) power allocated to the MCG for the DAPS operation, as described elsewhere herein with respect to certain embodiments. Any data bearers (including signalling radio bearer (SRB)) that are mapped to the MN may continue uninterrupted if they have a split leg configured via the SN.

Further, certain embodiments may include the UE releasing the source primary serving (PS) cell operation based on an uplink switch for a target PSCell to enable resumption of MN radio link monitoring. This operation may differ from DAPS operations where explicit source PS release may be used.

Certain embodiments described herein may provide enhancements to a handover of a UE with dual connectivity to a target cell with single connectivity. A source MN may inform a target MN to configure DAPS for selected SCG bearers, as part of a handover preparation. A MN may send a new X2/XN message to configure DAPS operation (e.g., a SN-DAPS-Config-Request or a SN-Modification-Request message) to configure the DAPS operation on selected SCG bearers. A MN may send a RRC reconfiguration message toward the UE to disable MCG operation on the master radio link between the UE and the MN and/or MN radio link monitoring, but configuring the DAPS for SCG bearers, which have source PS operation via the PSCell, with target PS operation via the target MN. In this case, the reconfiguration-related changes according to some embodiments may be related to radio link monitoring of MN and fall-back from DAPS to normal handover for specific situations.

Certain embodiments described herein may relate to DAPS operation for a SN- terminated split bearer. For example, certain embodiments may enable DAPS operation for a SN-terminated split bearer. After completion of handover preparation with a target node, the source MN may inform a source SN about a new parameter indicating that DAPS is to be started for a SCG split bearer in a message requesting SgNB release. On reception of the indication to start DAPS for SCG-split bearer, the SN may start forwarding packet data convergence protocol (PDCP) service data units (SDUs) or protocol data units (PDUs) to a forwarding Internet protocol (IP) address and may suspend the SCG operation. The SN may continue to send the PDCP SDUs or PDUs to a MN for sending via the source radio link during handover. The DAPS operation at the source MN may include one or more protocol stacks distributed between master and secondary nodes. The medium access control (MAC) and radio link control (RLC) layers of a source PS may operate over a source MN radio link between the source MN and a UE. In this case, the source PDCP of the DAPS operation may use a source eNB key (S-KeNB) for ciphering. Certain embodiments are described in more detail with respect to Figs. 4-1 lb.

Fig. 4 illustrates an example signal diagram of a MN-initiated SN change, according to some embodiments. Fig. 4 illustrates a UE, a MN (a source MN), a source SN, and a target SN (or MN in certain embodiments).

As illustrated at 400, the MN may transmit, and the target SN may receive, a secondary gNB (SgNB) addition request to add the target SN. For example, the request may include a DAPS request (“DAPS-Requesf ’) for selected SCG bearers. As illustrated at 402, the target SN may transmit, and the MN may receive, a SgNB addition request acknowledgement (ACK). For example, the ACK may include an RRC reconfiguration ACK (“RRC-Reconfig”) and may indicate that DAPS operations is to be used for the selected bearers, may include an indication to activate DAPS (“DAPS-Activation-Ind), and/or the like.

As illustrated at 404, the MN may transmit, and the source SN may receive, a SgNB release request. The release request may be associated with requesting release of the source SN as the SN to the MN and may include information similar to that described above at 400. As illustrated at 406, the source SN may transmit, and the MN may receive, a SgNB release request ACK. The release request ACK may be associated with acknowledging the release request and may include information similar to the ACK described above at 402.

As illustrated at 408, the MN may transmit, and the UE may receive, a RRC connection reconfiguration message. The RRC connection reconfiguration message may include a set of parameters that indicates information to the UE regarding the DAPS handover to be performed from the source SN to the target SN. For example, the parameters may indicate that DAPS operation over SCG is to be performed, a condition for DAPS activation (e.g., source and target SN radio quality, such as reference signal received power (RSRP)/reference signal received quality (RSRQ)/signal to interference and noise ratio (SINR), satisfying a threshold value of decibel-milliwatts (dBm)), a MN serving cell threshold condition for DAPS maintenance, and/or a PSCell threshold (e.g., for activation and/or maintenance of DAPS). As illustrated at 410, the UE and/or the MN may suspend MCG monitoring, including suspension of RLM.

As illustrated at 412, the UE may perform random access channel (RACH) access to the target SN. As illustrated at 414, the UE and the source SN may continue source PS operation during the RACH access. As illustrated at 416, the UE may transmit, and the target SN may receive, a PDCP DAPS uplink transmission switched to the target SN on the first uplink grant. For example, after the RACH access to the target SN and switching from the MN to the target SN, the UE may transmit uplink data to the target SN on the first uplink grant. As illustrated at 418, the target SN may transmit, and the UE may receive, a RRC reconfiguration message. For example, the RRC reconfiguration message may be associated with a source PS release at the source SN.

As described above, Fig. 4 is provided as an example. Other examples are possible, according to some embodiments. For example, Fig. 4 illustrates an example signal diagram of a MN-initiated SN change but a similar message sequence may also be applied for SN-initiated SN change or SN initiated PSCell change where the source and target SN are the same. Fig. 5 illustrates an example signal diagram depicting a DAPS handover of a UE having dual connectivity at a source MN and a SN, to a target MN, according to some embodiments. The target MN may be configured with single connectivity and DAPS may be configured for the SCG bearers of the source MN. Fig. 5 illustrates a UE, a MN (a source MN), a source SN, and a target MN (or SN in certain embodiments).

As illustrated at 500, the MN may transmit, and the target MN may receive, a handover request. For example, the handover request may include an indication to perform a DAPS handover (“DAPS-HO-Ind”) for SCG bearers. As illustrated at 502, the target MN may transmit, and the UE may receive, a handover request ACK. For example, the handover request ACK may include a RRC reconfiguration message (“RRC-Reconfig”) that includes a target configuration (cell group and/or radio bearer configuration of the target master cell group) and a source configuration (cell group and/or radio bearer configuration of the source radio link) modified to work with a SCG. As illustrated at 504, the MN may transmit, and the source SN may receive, a request to release the SN (“SgNB-Release-Request”). For example, the request may include a DAPS configuration for selected SCG bearers, which indicates the SCG to transmit packets via the secondary radio link and also forward packets to the target MN for the DAPS operation. As illustrated at 506, the MN may transmit, and the UE may receive, a RRC connection reconfiguration message. The RRC connection reconfiguration message may include a set of parameters related to performing a DAPS handover. For example, the set of parameters may include a parameter that indicates that a DAPS handover (HO) is configured for a SCG (“DAPS HO configured for SCG”), a parameter that indicates a condition for activating the DAPS operation (“DAPS activation condition”), and/or a parameter that indicates a condition for maintaining DAPS operation (“DAPS maintenance condition”).

As illustrated at 508, the UE and the MN may suspend source MCG operation, including RLM. As illustrated at 510, the UE and the source SN may use SCG bearer DAPS operation as source PS. As illustrated at 512, the UE may perform, to the target MN, RACH access procedures and handover completion to the target MN. As illustrated at 514, the target MN may transmit, and the UE may receive, a RRC reconfiguration message (“RRC-Reconfiguration”). For example, the message may be associated with releasing the source PS.

As described above, Fig. 5 is provided as an example. Other examples are possible, according to some embodiments.

Fig. 6 illustrates an example of a PDCP state transition for MN/SN-initiated PSCell change with DAPS, according to some embodiments. For example, this state transition may be used for DAPS operation for certain embodiments. As illustrated in Fig. 6, a UE may utilize a single protocol stack before PSCell change, a dual protocol stack during a PSCell change execution window, and another single protocol stack after successful PSCell change. As illustrated at 600, the UE may switch from using the single protocol stack before the PSCell change to using the dual protocol stack based on receiving an indication to implement a DAPS PSCell change. As illustrated at 610, the UE may switch from using the dual protocol stack to using the other single protocol stack after successful PSCell change based on receiving an indication to release the source PSCell.

As described above, Fig. 6 is provided as an example. Other examples are possible, according to some embodiments.

Fig. 7 illustrates an example of a PDCP state transition handover from a MN to a gNB/eNB with DAPS configured for SCG bearers, according to some embodiments. For example, this state transition may be used for DAPS operation for certain embodiments. As illustrated in Fig. 7, a UE may utilize a single protocol stack before DAPS handover, a dual protocol stack during a PSCell change execution window, and another single protocol stack after successful PSCell change. As illustrated at 700, the UE may switch from using the single protocol stack before the DAPS handover to using the dual protocol stack based on receiving a RRC reconfiguration message (“RRC Reconfig”). For example, the RRC reconfiguration message may indicate to implement DAPS on a source SCG. As illustrated at 710, the UE may switch from using the dual protocol stack to using the other single protocol stack after successful PSCell change based on receiving an indication to release the source PSCell.

As described above, Fig. 7 is provided as an example. Other examples are possible, according to some embodiments.

Fig. 8 illustrates an example of UE DAPS operations over a secondary radio link, according to some embodiments. As illustrated at 800, the UE may receive a RRC reconfiguration message for secondary radio link mobility with DAPS operation over a source secondary radio link and a target secondary radio link. For example, the UE may receive a RRC reconfiguration message from a MN, where the RRC reconfiguration message indicates that DAPS operation is to be used for secondary radio link mobility (e.g., a change in a secondary radio link from a source secondary radio link at a source SN to a target secondary radio link at a target SN). These operations may be similar to, for example, those described above at 408, 506, 600, and/or 700.

As illustrated at 802, if the received RRC reconfiguration message includes a primary cell (Pcell) threshold for DAPS operation, then the UE may check a master radio link status relative to the threshold. For example, the UE may determine whether the RRC reconfiguration message includes a parameter that indicates a parameter for a Pcell threshold for implementing DAPS operation (e.g., the parameter may be similar to those described above at 408 and/or 506). If the RRC reconfiguration message includes the Pcell threshold, then the UE may determine whether a master radio link status satisfies the Pcell threshold (e.g., the UE may determine whether a condition on the master radio link satisfies the Pcell threshold).

As illustrated at 804, if the master link radio status fails to satisfy the threshold, at 804- NO, then the UE may continue to monitor the master radio link status relative to the Pcell threshold. As further illustrated at 804, if the master radio link status satisfies the threshold, at 804-YES, then the UE may, at 806, start DAPS operation over the secondary radio link and may suspend the master radio link. For example, the UE may activate the DAPS operation by activating dual protocol stacks, as described above at 600 and/or 700. Additionally, or alternatively, the UE may suspend operations on the source master radio link, in a manner similar to that described above at 410 and/or 508.

As illustrated at 808, the UE may determine whether a relative radio condition was provided in a parameter in the RRC reconfiguration message. For example, the parameter may indicate the relative radio condition and may be similar to that described above at 408 and/or 506. As illustrated at 810, if the RRC reconfiguration message includes information identifying the relative radio condition, at 808-YES, then the UE may adjust, based on the relative radio condition, secondary radio link measurements (e.g., PSCell reference signal measurements, such as RSRP measurements) on a secondary radio link at the target SN. For example, the relative radio condition may identify a difference between condition-related measurements on the secondary radio link to the target SN and condition-related measurements on the secondary radio link to the source SN, and the UE may adjust measurements on the secondary radio link to the target SN based on these differences. In some embodiments, the UE may not perform the operations at 808 and 810 if the relative radio condition was not provided in the parameter, and may perform the operations at 812 after performing the operations at 806. As illustrated at 812, the UE may determine whether a timer for SCG DAPS operation has expired. For example, the timer may be a parameter included in the RRC reconfiguration message, similar to that described above at 408 and 506. The timer may indicate a time -period (e.g., an execution window) during which the UE can use the DAPS operation, similar to that described in Figs. 6 and 7. If the UE determines that the timer is not expired (812-NO), then the UE may continue to monitor the timer (e.g., continuously or periodically), and may continue to use the DAPS operation. If the UE determines that the timer has expired (812-YES), then the UE may, at 814, terminate the DAPS handover and may resume MCG monitoring. For example, the UE may terminate use of dual protocol stacks, in a manner similar to that described above at 610 and 710, and/or may continue monitoring the source master radio link between the UE and the source MN.

As described above, Fig. 8 is provided as an example. Other examples are possible, according to some embodiments.

Fig. 9 illustrates an example flow diagram of a method, according to some embodiments. For example, Fig. 9 shows example operations of a UE (e.g., apparatus 20). Some of the operations illustrated in Fig. 9 may be similar to some operations shown in, or described with respect to, Figs. 1-8.

As context, the method illustrated in Fig. 9 may be for a handover from a source master node to a target master node in dual connectivity, where the UE has a connection with a master radio link to the source master node and a secondary radio link to a source secondary node. In an embodiment, the method may include, at 900, receiving, from the source master node, a message associated with triggering radio link measurements with the secondary radio link during a suspension of the connection with the source master node (e.g., in a manner similar to that described at 506). In an embodiment, the method may include, at 902, suspending the connection between the UE and the source master node (e.g., in a manner similar to that described at 508). In an embodiment, the method may include, at 904, activating dual active protocol stack operation for data transmission at the UE with the secondary radio link and a target radio link to the target master node (e.g., in a manner similar to that described at 508).

In some embodiments, the message may include RRC configuration signaling. In some embodiments, the message may include one or more parameters related to at least one of a source radio condition threshold, of the master radio link, for starting the handover, use of a radio condition difference to adjust secondary RLM, or a timer to complete the dual active protocol stack operation for a SCG.

In some embodiments, the method may further include receiving, from the target master node, a message associated with releasing the source master node (e.g., in a manner similar to that described at 514). In some embodiments, the method may further include deactivating the dual active protocol stack operation based on the message associated with releasing the serving master node. In some embodiments, the message associated with releasing the source master node may include RRC reconfiguration signaling.

In some embodiments, the method may include performing, based on activating the dual active protocol stack operation, a PDCP-dual active protocol stack uplink transmission to the target master node on a first uplink grant. In some embodiments, the method may include performing, based on activating the dual active protocol stack operation, a RACH procedure (e.g., in a manner similar to that described at 512). In some embodiments, the method may include completing the handover based on performing the RACH procedure (e.g., in a manner similar to that described at 512).

In some embodiments, the method may further include checking a status of the master radio link relative to a threshold based on receiving the message (e.g., in a manner similar to that described at 802). In some embodiments, the suspending or the activating may be based on the status of the master radio link satisfying the threshold (e.g., in a manner similar to that described at 806). In some embodiments, the method may further include adjusting the radio link measurements for the secondary radio link based on a source radio condition offset indicated in the message (e.g., in a manner similar to that described at 810). In some embodiments, the method may include, based on expiration of a timer, terminating the handover, or resuming MCG monitoring (e.g., in a manner similar to that described at 814).

As described above, Fig. 9 is provided as an example. Other examples are possible according to some embodiments.

Fig. 10 illustrates an example flow diagram of a method, according to some embodiments. For example, Fig. 10 shows example operations of a network node (a master node or source master node) (e.g., apparatus 10). Some of the operations illustrated in Fig. 10 may be similar to some operations shown in, or described with respect to, Figs. 1-8.

As context, the method illustrated in Fig. 10 may be for a handover from a source master node to a target master node in dual connectivity, where the UE has a connection with a master radio link to the source master node and a secondary radio link to a source secondary node. In an embodiment, the method may include at 1000, transmitting, to the source secondary node or to the target master node, a request related to activating the handover. In an embodiment, the method may include, at 1002, transmitting, to the UE, a message (e.g., in a manner similar to that described at 506). The message may be associated with triggering radio link measurements with the secondary radio link during a suspension of the connection with the source master node. In an embodiment, the method may include, at 1004, suspending the connection between the UE and the source master node (e.g., in a manner similar to that described at 508).

In some embodiments, operations of the source master node associated with a dual active protocol stack may be distributed between the source master node and the source secondary node. In some embodiments, the method may further include transmitting, to the source secondary node, an indication that the user equipment (UE) is to activate a dual active protocol stack operation. In some embodiments, the indication may be associated with causing the source secondary node to start forwarding one or more packets to the target master node and to continue scheduling via the source master node while suspending a transmission via the source secondary node.

In some embodiments, the method may further include transmitting, to the UE, an indication associated with causing the DAPS operation to be activated (e.g., in a manner similar to that described at 600 and/or 700). In some embodiments, the method may further include transmitting, to the UE, another indication associated with causing the DAPS operation to be deactivated (e.g., in a manner similar to that described at 610 and/or 710).

As described above, Fig. 10 is provided as an example. Other examples are possible according to some embodiments.

Fig. 11a illustrates an example of an apparatus 10 according to an embodiment. In an embodiment, apparatus 10 may be a node, host, or server in a communications network or serving such a network. For example, apparatus 10 may be a network node, satellite, base station, a Node B, an evolved Node B (eNB), 5G Node B or access point, next generation Node B (NG-NB or gNB), and/or a WEAN access point, associated with a radio access network, such as a FTE network, 5G or NR. In example embodiments, apparatus 10 may be an eNB in FTE or gNB in 5G. Apparatus 10 may include, or host, a MN and/or a SN, as described elsewhere herein. It should be understood that, in some example embodiments, apparatus 10 may be comprised of an edge cloud server as a distributed computing system where the server and the radio node may be stand-alone apparatuses communicating with each other via a radio path or via a wired connection, or they may be located in a same entity communicating via a wired connection. For instance, in certain example embodiments where apparatus 10 represents a gNB, it may be configured in a central unit (CU) and distributed unit (DU) architecture that divides the gNB functionality. In such an architecture, the CU may be a logical node that includes gNB functions such as transfer of user data, mobility control, radio access network sharing, positioning, and/or session management, etc. The CU may control the operation of DU(s) over a front-haul interface. The DU may be a logical node that includes a subset of the gNB functions, depending on the functional split option. It should be noted that one of ordinary skill in the art would understand that apparatus 10 may include components or features not shown in Fig. 1 la.

As illustrated in the example of Fig. 1 la, apparatus 10 may include a processor 12 for processing information and executing instructions or operations. Processor 12 may be any type of general or specific purpose processor. In fact, processor 12 may include one or more of general-purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs), field-programmable gate arrays (FPGAs), application-specific integrated circuits (ASICs), and processors based on a multi-core processor architecture, as examples. While a single processor 12 is shown in Fig. 1 la, multiple processors may be utilized according to other embodiments. For example, it should be understood that, in certain embodiments, apparatus 10 may include two or more processors that may form a multiprocessor system (e.g., in this case processor 12 may represent a multiprocessor) that may support multiprocessing. In certain embodiments, the multiprocessor system may be tightly coupled or loosely coupled (e.g., to form a computer cluster).

Processor 12 may perform functions associated with the operation of apparatus 10, which may include, for example, precoding of antenna gain/phase parameters, encoding and decoding of individual bits forming a communication message, formatting of information, and overall control of the apparatus 10, including processes related to management of communication resources. Apparatus 10 may further include or be coupled to a memory 14 (internal or external), which may be coupled to processor 12, for storing information and instructions that may be executed by processor 12. Memory 14 may be one or more memories and of any type suitable to the local application environment, and may be implemented using any suitable volatile or nonvolatile data storage technology such as a semiconductor-based memory device, a magnetic memory device and system, an optical memory device and system, fixed memory, and/or removable memory. For example, memory 14 can be comprised of any combination of random access memory (RAM), read only memory (ROM), static storage such as a magnetic or optical disk, hard disk drive (HDD), or any other type of non-transitory machine or computer readable media. The instructions stored in memory 14 may include program instructions or computer program code that, when executed by processor 12, enable the apparatus 10 to perform tasks as described herein.

In an embodiment, apparatus 10 may further include or be coupled to (internal or external) a drive or port that is configured to accept and read an external computer readable storage medium, such as an optical disc, USB drive, flash drive, or any other storage medium. For example, the external computer readable storage medium may store a computer program or software for execution by processor 12 and/or apparatus

10.

In some embodiments, apparatus 10 may also include or be coupled to one or more antennas 15 for transmitting and receiving signals and/or data to and from apparatus 10. Apparatus 10 may further include or be coupled to a transceiver 18 configured to transmit and receive information. The transceiver 18 may include, for example, a plurality of radio interfaces that may be coupled to the antenna(s) 15. The radio interfaces may correspond to a plurality of radio access technologies including one or more of GSM, NB-IoT, LTE, 5G, WLAN, Bluetooth, BT-LE, NFC, radio frequency identifier (RFID), ultrawideband (UWB), MulteFire, and the like. The radio interface may include components, such as filters, converters (for example, digital-to-analog converters and the like), mappers, a Fast Fourier Transform (FFT) module, and the like, to generate symbols for a transmission via one or more downlinks and to receive symbols (for example, via an uplink).

As such, transceiver 18 may be configured to modulate information on to a carrier waveform for transmission by the antenna(s) 15 and demodulate information received via the antenna(s) 15 for further processing by other elements of apparatus 10. In other embodiments, transceiver 18 may be capable of transmitting and receiving signals or data directly. Additionally or alternatively, in some embodiments, apparatus 10 may include an input and/or output device (I/O device).

In an embodiment, memory 14 may store software modules that provide functionality when executed by processor 12. The modules may include, for example, an operating system that provides operating system functionality for apparatus 10. The memory may also store one or more functional modules, such as an application or program, to provide additional functionality for apparatus 10. The components of apparatus 10 may be implemented in hardware, or as any suitable combination of hardware and software.

According to some embodiments, processor 12 and memory 14 may be included in or may form a part of processing circuitry or control circuitry. In addition, in some embodiments, transceiver 18 may be included in or may form a part of transceiver circuitry.

As used herein, the term “circuitry” may refer to hardware-only circuitry implementations (e.g., analog and/or digital circuitry), combinations of hardware circuits and software, combinations of analog and/or digital hardware circuits with software/firmware, any portions of hardware processor(s) with software (including digital signal processors) that work together to case an apparatus (e.g., apparatus 10) to perform various functions, and/or hardware circuit(s) and/or processor(s), or portions thereof, that use software for operation but where the software may not be present when it is not needed for operation. As a further example, as used herein, the term “circuitry” may also cover an implementation of merely a hardware circuit or processor (or multiple processors), or portion of a hardware circuit or processor, and its accompanying software and/or firmware. The term circuitry may also cover, for example, a baseband integrated circuit in a server, cellular network node or device, or other computing or network device.

As introduced above, in certain embodiments, apparatus 10 may be a network node or RAN node, such as a base station, access point, Node B, eNB, gNB, WLAN access point, or the like.

According to certain embodiments, apparatus 10 may be controlled by memory 14 and processor 12 to perform the functions associated with any of the embodiments described herein, such as some operations described with respect to Figs. 1-3 or illustrated in, and described with respect to, Figs. 4-10.

For instance, in one embodiment, apparatus 10 may be controlled by memory 14 and processor 12 to transmit, to the UE, a message. The message may be associated with triggering radio link measurements with the secondary radio link during a suspension of the connection with the source master node. In one embodiment, apparatus 10 may be controlled by memory 14 and processor 12 to suspend the connection between the UE and the source master node.

Fig. l ib illustrates an example of an apparatus 20 according to another embodiment. In an embodiment, apparatus 20 may be a node or element in a communications network or associated with such a network, such as a UE, mobile equipment (ME), mobile station, mobile device, stationary device, IoT device, or other device. As described herein, a UE may alternatively be referred to as, for example, a mobile station, mobile equipment, mobile unit, mobile device, user device, subscriber station, wireless terminal, tablet, smart phone, IoT device, sensor or NB-IoT device, or the like. As one example, apparatus 20 may be implemented in, for instance, a wireless handheld device, a wireless plug-in accessory, or the like. In some example embodiments, apparatus 20 may include one or more processors, one or more computer-readable storage medium (for example, memory, storage, or the like), one or more radio access components (for example, a modem, a transceiver, or the like), and/or a user interface. In some embodiments, apparatus 20 may be configured to operate using one or more radio access technologies, such as GSM, LTE, LTE-A, NR, 5G, WLAN, WiFi, NB-IoT, Bluetooth, NFC, MulteFire, and/or any other radio access technologies. It should be noted that one of ordinary skill in the art would understand that apparatus 20 may include components or features not shown in Fig. 1 lb.

As illustrated in the example of Fig. 1 lb, apparatus 20 may include or be coupled to a processor 22 for processing information and executing instructions or operations. Processor 22 may be any type of general or specific purpose processor. In fact, processor 22 may include one or more of general-purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs), field-programmable gate arrays (FPGAs), application-specific integrated circuits (ASICs), and processors based on a multi-core processor architecture, as examples. While a single processor 22 is shown in Fig. 1 lb, multiple processors may be utilized according to other embodiments. For example, it should be understood that, in certain embodiments, apparatus 20 may include two or more processors that may form a multiprocessor system (e.g., in this case processor 22 may represent a multiprocessor) that may support multiprocessing. In certain embodiments, the multiprocessor system may be tightly coupled or loosely coupled (e.g., to form a computer cluster).

Processor 22 may perform functions associated with the operation of apparatus 20 including, as some examples, precoding of antenna gain/phase parameters, encoding and decoding of individual bits forming a communication message, formatting of information, and overall control of the apparatus 20, including processes related to management of communication resources.

Apparatus 20 may further include or be coupled to a memory 24 (internal or external), which may be coupled to processor 22, for storing information and instructions that may be executed by processor 22. Memory 24 may be one or more memories and of any type suitable to the local application environment, and may be implemented using any suitable volatile or nonvolatile data storage technology such as a semiconductor-based memory device, a magnetic memory device and system, an optical memory device and system, fixed memory, and/or removable memory. For example, memory 24 can be comprised of any combination of random access memory (RAM), read only memory (ROM), static storage such as a magnetic or optical disk, hard disk drive (HDD), or any other type of non-transitory machine or computer readable media. The instructions stored in memory 24 may include program instructions or computer program code that, when executed by processor 22, enable the apparatus 20 to perform tasks as described herein.

In an embodiment, apparatus 20 may further include or be coupled to (internal or external) a drive or port that is configured to accept and read an external computer readable storage medium, such as an optical disc, USB drive, flash drive, or any other storage medium. For example, the external computer readable storage medium may store a computer program or software for execution by processor 22 and/or apparatus 20. In some embodiments, apparatus 20 may also include or be coupled to one or more antennas 25 for receiving a downlink signal and for transmitting via an uplink from apparatus 20. Apparatus 20 may further include a transceiver 28 configured to transmit and receive information. The transceiver 28 may also include a radio interface (e.g., a modem) coupled to the antenna 25. The radio interface may correspond to a plurality of radio access technologies including one or more of GSM, LTE, LTE-A, 5G, NR, WLAN, NB-IoT, Bluetooth, BT-LE, NFC, RFID, UWB, and the like. The radio interface may include other components, such as filters, converters (for example, digital-to-analog converters and the like), symbol demappers, signal shaping components, an Inverse Fast Fourier Transform (IFFT) module, and the like, to process symbols, such as OFDMA symbols, carried by a downlink or an uplink. For instance, transceiver 28 may be configured to modulate information on to a carrier waveform for transmission by the antenna(s) 25 and demodulate information received via the antenna(s) 25 for further processing by other elements of apparatus 20. In other embodiments, transceiver 28 may be capable of transmitting and receiving signals or data directly. Additionally or alternatively, in some embodiments, apparatus 20 may include an input and/or output device (I/O device). In certain embodiments, apparatus 20 may further include a user interface, such as a graphical user interface or touchscreen.

In an embodiment, memory 24 stores software modules that provide functionality when executed by processor 22. The modules may include, for example, an operating system that provides operating system functionality for apparatus 20. The memory may also store one or more functional modules, such as an application or program, to provide additional functionality for apparatus 20. The components of apparatus 20 may be implemented in hardware, or as any suitable combination of hardware and software. According to an example embodiment, apparatus 20 may optionally be configured to communicate with apparatus 10 via a wireless or wired communications link 70 according to any radio access technology, such as NR.

According to some embodiments, processor 22 and memory 24 may be included in or may form a part of processing circuitry or control circuitry. In addition, in some embodiments, transceiver 28 may be included in or may form a part of transceiving circuitry.

As discussed above, according to some embodiments, apparatus 20 may be a UE, mobile device, mobile station, ME, IoT device and/or NB-IoT device, for example. According to certain embodiments, apparatus 20 may be controlled by memory 24 and processor 22 to perform the functions associated with example embodiments described herein. For example, in some embodiments, apparatus 20 may be configured to perform one or more of the processes described with respect to Figs. 1-3 or illustrated in, and described with respect to, Figs. 4-10. For instance, in one embodiment, apparatus 20 may be controlled by memory 24 and processor 22 to receive, from the source master node, a message associated with triggering radio link measurements with the secondary radio link during a suspension of the connection with the source master node. In one embodiment, apparatus 20 may be controlled by memory 24 and processor 22 to suspend the connection between the user equipment (UE) and the source master node activating dual active protocol stack operation for data transmission at the user equipment (UE) with the secondary radio link and a target radio link to the target master node.

Therefore, certain example embodiments provide several technological improvements, enhancements, and/or advantages over existing technological processes. For example, one benefit of some example embodiments is a handover from a source master node to a target master node in dual connectivity, where a UE has a connection with a master radio link to the source master node and a secondary radio link to a source secondary node. Accordingly, the use of some example embodiments results in improved functioning of communications networks and their nodes and, therefore constitute an improvement at least to the technological field of DAPS handover, among others.

In some example embodiments, the functionality of any of the methods, processes, signaling diagrams, algorithms or flow charts described herein may be implemented by software and/or computer program code or portions of code stored in memory or other computer readable or tangible media, and executed by a processor.

In some example embodiments, an apparatus may be included or be associated with at least one software application, module, unit or entity configured as arithmetic operation(s), or as a program or portions of it (including an added or updated software routine), executed by at least one operation processor. Programs, also called program products or computer programs, including software routines, applets and macros, may be stored in any apparatus-readable data storage medium and may include program instructions to perform particular tasks. A computer program product may include one or more computer-executable components which, when the program is run, are configured to carry out some example embodiments. The one or more computer-executable components may be at least one software code or portions of code. Modifications and configurations used for implementing functionality of an example embodiment may be performed as routine(s), which may be implemented as added or updated software routine(s). In one example, software routine(s) may be downloaded into the apparatus.

As an example, software or a computer program code or portions of code may be in a source code form, object code form, or in some intermediate form, and it may be stored in some sort of carrier, distribution medium, or computer readable medium, which may be any entity or device capable of carrying the program. Such carriers may include a record medium, computer memory, read-only memory, photoelectrical and/or electrical carrier signal, telecommunications signal, and/or software distribution package, for example. Depending on the processing power needed, the computer program may be executed in a single electronic digital computer or it may be distributed amongst a number of computers. The computer readable medium or computer readable storage medium may be a non-transitory medium.

In other example embodiments, the functionality may be performed by hardware or circuitry included in an apparatus (e.g., apparatus 10 or apparatus 20), for example through the use of an application specific integrated circuit (ASIC), a programmable gate array (PGA), a field programmable gate array (FPGA), or any other combination of hardware and software. In yet another example embodiment, the functionality may be implemented as a signal, such as a non-tangible means that can be carried by an electromagnetic signal downloaded from the Internet or other network.

According to an example embodiment, an apparatus, such as a node, device, or a corresponding component, may be configured as circuitry, a computer or a microprocessor, such as single-chip computer element, or as a chipset, which may include at least a memory for providing storage capacity used for arithmetic operation(s) and/or an operation processor for executing the arithmetic operation(s). Example embodiments described herein apply equally to both singular and plural implementations, regardless of whether singular or plural language is used in connection with describing certain embodiments. For example, an embodiment that describes operations of a single network node equally applies to embodiments that include multiple instances of the network node, and vice versa.

One having ordinary skill in the art will readily understand that the example embodiments as discussed above may be practiced with operations in a different order, and/or with hardware elements in configurations which are different than those which are disclosed. Therefore, although some embodiments have been described based upon these example preferred embodiments, it would be apparent to those of skill in the art that certain modifications, variations, and alternative constructions would be apparent, while remaining within the spirit and scope of example embodiments.

PARTIAL GLOSSARY MCG Master Cell Group

SCG Secondary Cell Group

NR New Radio

DCCA Dual Connectivity Carrier Aggregation

DC Dual Connectivity CA Carrier Aggregation

RRC Radio Resource Control

DL Downlink

SRB Signalling Radio Bearer

SN Secondary Node MN Master Node

Claims

CLAIMS:

1. A method, comprising: for a handover from a source master node to a target master node in dual connectivity, wherein a user equipment (UE) has a connection with a master radio link to the source master node and a secondary radio link to a source secondary node: receiving, by the user equipment (UE) from the source master node, a message associated with triggering radio link measurements with the secondary radio link during a suspension of the connection with the source master node; suspending the connection between the user equipment (UE) and the source master node; and activating dual active protocol stack operation for data transmission at the user equipment (UE) with the secondary radio link and a target radio link to the target master node.

2. The method according to claim 1, wherein the message comprises radio resources control (RRC) configuration signaling.

3. The method according to claims 1 or 2, wherein the message comprises one or more parameters related to at least one of: a source radio condition threshold, of the master radio link, for starting the handover, use of a radio condition difference to adjust secondary radio link management (RLM), or a timer to complete the dual active protocol stack operation for a secondary cell group (SCG).

4. The method according to one or more of claims 1-3, further comprising: receiving, from the target master node, a message associated with releasing the source master node.

5. The method according to claim 4, further comprising: deactivating the dual active protocol stack operation based on the message associated with releasing the serving master node.

6. The method according to claim 4, wherein the message associated with releasing the source master node comprises radio resource control (RRC) reconfiguration signaling.

7. The method according to one or more of claims 1-6, further comprising: performing, based on activating the dual active protocol stack operation, a packet data convergence protocol (PDCP)-dual active protocol stack uplink transmission to the target master node on a first uplink grant.

8. The method according to one or more of claims 1-7, further comprising: performing, based on activating the dual active protocol stack operation, a random access channel (RACH) procedure; and completing the handover based on performing the random access channel (RACH) procedure.

9. The method according to one or more of claims 1-8, further comprising: checking a status of the master radio link relative to a threshold based on receiving the message.

10. The method according to claim 9, wherein the suspending or the activating is based on the status of the master radio link satisfying the threshold.

11. The method according to claim 10, further comprising: adjusting the radio link measurements for the secondary radio link based on a source radio condition offset indicated in the message.

12. The method according to claim 11, further comprising: based on expiration of a timer: terminating the handover, or resuming master cell group (MCG) monitoring.

13. A method, comprising: for a handover from a source master node to a target master node in dual connectivity, wherein a user equipment (UE) has a connection with a master radio link to the source master node and a secondary radio link to a source secondary node: transmitting, by the source master node to the user equipment (UE), a message, wherein the message is associated with triggering radio link measurements with the secondary radio link during a suspension of the connection with the source master node; and suspending the connection between the user equipment (UE) and the source master node.

14. The method according to claim 13, wherein the message comprises radio resources control (RRC) configuration signaling.

15. The method according to claims 13 or 14, wherein the message comprises one or more parameters related to at least one of: a source radio condition threshold, of the master radio link, for starting the handover, use of a radio condition difference to adjust secondary radio link management (RLM), or a timer to complete the dual active protocol stack operation for a secondary cell group (SCG).

16. The method according to one or more of claims 13-15, wherein operations of the source master node associated with a dual active protocol stack are distributed between the source master node and the source secondary node.

17. The method according to one or more of claims 13-16, further comprising: transmitting, to the source secondary node, an indication that the user equipment (UE) is to activate a dual active protocol stack operation, wherein the indication is associated with causing the source secondary node to start forwarding one or more packets to the target master node and to continue scheduling via the source master node while suspending a transmission via the source secondary node.

18. The method according to one or more of claims 13-17, further comprising: transmitting, to the UE, an indication associated with causing the dual active protocol stack (DAPS) operation to be activated, or transmitting, to the UE, another indication associated with causing the dual active protocol stack (DAPS) operation to be deactivated.

19. An apparatus, comprising: at least one processor; and at least one memory including computer program code, wherein the at least one memory and the computer program code are configured to, with the at least one processor, cause the apparatus at least to for a handover from a source master node to a target master node in dual connectivity, wherein the apparatus has a connection with a master radio link to the source master node and a secondary radio link to a source secondary node: receive, from the source master node, a message associated with triggering radio link measurements with the secondary radio link during a suspension of the connection with the source master node; suspend the connection between the apparatus and the source master node; and activate dual active protocol stack operation for data transmission at the apparatus with the secondary radio link and a target radio link to the target master node.

20. The apparatus according to claim 19, wherein the message comprises radio resources control (RRC) configuration signaling.

21. The apparatus according to claims 19 or 20, wherein the message comprises one or more parameters related to at least one of: a source radio condition threshold, of the master radio link, for starting the handover, use of a radio condition difference to adjust secondary radio link management (RLM), or a timer to complete the dual active protocol stack operation for a secondary cell group (SCG).

22. The apparatus according to one or more of claims 19-21, wherein the at least one memory and the computer program code are configured to, with the at least one processor, further cause the apparatus at least to: receive, from the target master node, a message associated with releasing the source master node.

23. The apparatus according to claim 22, wherein the at least one memory and the computer program code are configured to, with the at least one processor, further cause the apparatus at least to: deactivate the dual active protocol stack operation based on the message associated with releasing the serving master node.

24. The apparatus according to claim 22, wherein the message associated with releasing the source master node comprises radio resource control (RRC) reconfiguration signaling.

25. The apparatus according to one or more of claims 19-24, wherein the at least one memory and the computer program code are configured to, with the at least one processor, further cause the apparatus at least to: perform, based on activating the dual active protocol stack operation, a packet data convergence protocol (PDCP)-dual active protocol stack uplink transmission to the target master node on a first uplink grant.

26. The apparatus according to one or more of claims 19-25, wherein the at least one memory and the computer program code are configured to, with the at least one processor, further cause the apparatus at least to: perform, based on activating the dual active protocol stack operation, a random access channel (RACH) procedure; and complete the handover based on performing the random access channel (RACH) procedure.

27. The apparatus according to one or more of claims 19-26, wherein the at least one memory and the computer program code are configured to, with the at least one processor, further cause the apparatus at least to: check a status of the master radio link relative to a threshold based on receiving the message.

28. The apparatus according to claim 27, wherein the suspending or the activating is based on the status of the master radio link satisfying the threshold.

29. The apparatus according to claim 28, wherein the at least one memory and the computer program code are configured to, with the at least one processor, further cause the apparatus at least to: adjust the radio link measurements for the secondary radio link based on a source radio condition offset indicated in the message.

30. The apparatus according to claim 29, wherein the at least one memory and the computer program code are configured to, with the at least one processor, further cause the apparatus at least to: based on expiration of a timer: terminate the handover, or resume master cell group (MCG) monitoring.

31. An apparatus, comprising: at least one processor; and at least one memory including computer program code, wherein the at least one memory and the computer program code are configured to, with the at least one processor, cause the apparatus at least to for a handover from the apparatus to a target master node in dual connectivity, wherein a user equipment (UE) has a connection with a master radio link to the apparatus and a secondary radio link to a source secondary node: transmit, to the user equipment (UE), a message, wherein the message is associated with triggering radio link measurements with the secondary radio link during a suspension of the connection with the apparatus; and suspend the connection between the user equipment (UE) and the apparatus.

32. The apparatus according to claim 31, wherein the message comprises radio resources control (RRC) configuration signaling.

33. The apparatus according to claims 31 or 32, wherein the message comprises one or more parameters related to at least one of: a source radio condition threshold, of the master radio link, for starting the handover, use of a radio condition difference to adjust secondary radio link management (RLM), or a timer to complete the dual active protocol stack operation for a secondary cell group (SCG).

34. The apparatus according to one or more of claims 31-33, wherein operations of the apparatus associated with a dual active protocol stack are distributed between the apparatus and the source secondary node.

35. The apparatus according to one or more of claims 31-34, wherein the at least one memory and the computer program code are configured to, with the at least one processor, further cause the apparatus at least to: transmit, to the source secondary node, an indication that the user equipment (UE) is to activate a dual active protocol stack operation, wherein the indication is associated with causing the source secondary node to start forwarding one or more packets to the target master node and to continue scheduling via the apparatus while suspending a transmission via the source secondary node.

36. The apparatus according to one or more of claims 31-35, wherein the at least one memory and the computer program code are configured to, with the at least one processor, further cause the apparatus at least to: transmit, to the UE, an indication associated with causing the dual active protocol stack (DAPS) operation to be activated, or transmit, to the UE, another indication associated with causing the dual active protocol stack (DAPS) operation to be deactivated.

37. An apparatus, comprising: at least one processor; and at least one memory including computer program code, wherein the at least one memory and the computer program code are configured to, with the at least one processor, cause the apparatus at least to for a handover from a source secondary node to a target secondary node in dual connectivity, wherein the apparatus has a connection with a master radio link to a source master node and a secondary radio link to the source secondary node: receive, from the source master node, a message that indicates that the handover is to be performed; suspend the connection between the apparatus and the source master node; and activate dual active protocol stack operation for data transmission at the apparatus with the secondary radio link and a target radio link to the target secondary node.

38. The apparatus according to claim 37, wherein the message comprises radio resources control (RRC) configuration signaling.

39. The apparatus according to claims 37 or 38, wherein the message comprises one or more parameters related to at least one of: a source radio condition threshold, of the master radio link, for starting the handover, use of a radio condition difference to adjust secondary radio link management (RLM), or a timer to complete the dual active protocol stack operation for a secondary cell group (SCG).

40. The apparatus according to one or more of claims 37-39, wherein the at least one memory and the computer program code are configured to, with the at least one processor, further cause the apparatus at least to: receive, from the target secondary node, a message associated with releasing the source secondary node.

41. The apparatus according to claim 40, wherein the at least one memory and the computer program code are configured to, with the at least one processor, further cause the apparatus at least to: deactivate the dual active protocol stack operation based on the message associated with releasing the source secondary node.

42. The apparatus according to claim 40, wherein the message associated with releasing the source secondary node comprises radio resource control (RRC) reconfiguration signaling.

43. The apparatus according to one or more of claims 37-42, wherein the suspending or the activating is based on a status of the master radio link satisfying a threshold.

44. The apparatus according to one or more of claims 37-43, wherein the at least one memory and the computer program code are configured to, with the at least one processor, further cause the apparatus at least to: based on expiration of a timer: terminate the handover, or resume master cell group (MCG) monitoring.

45. A method, comprising: for a handover from a source secondary node to a target secondary node in dual connectivity, wherein a user equipment (UE) has a connection with a master radio link to a source master node and a secondary radio link to the source secondary node: receiving, from the source master node, a message that indicates that the handover is to be performed; suspending the connection between the user equipment (UE) and the source master node; and activating dual active protocol stack operation for data transmission at the user equipment (UE) with the secondary radio link and a target radio link to the target secondary node.

46. The method according to claim 45, wherein the message comprises radio resources control (RRC) configuration signaling.

47. The method according to claims 45 or 46, wherein the message comprises one or more parameters related to at least one of: a source radio condition threshold, of the master radio link, for starting the handover, use of a radio condition difference to adjust secondary radio link management (RLM), or a timer to complete the dual active protocol stack operation for a secondary cell group (SCG).

48. The method according to one or more of claims 45-47, further comprising receiving, from the target secondary node, a message associated with releasing the source secondary node.

49. The method according to claim 48, further comprising: deactivating the dual active protocol stack operation based on the message associated with releasing the source secondary node.

50. The method according to claim 48, wherein the message associated with releasing the source secondary node comprises radio resource control (RRC) reconfiguration signaling.

51. The method according to one or more of claims 45-50, wherein the suspending or the activating is based on a status of the master radio link satisfying a threshold.

52. The method according to one or more of claims 45-51, further comprising: based on expiration of a timer: terminating the handover, or resuming master cell group (MCG) monitoring.

53. An apparatus, comprising: for a handover from a source master node to a target master node in dual connectivity, wherein a user equipment (UE) has a connection with a master radio link to the source master node and a secondary radio link to a source secondary node: means for receiving, by the user equipment (UE) from the source master node, a message associated with triggering radio link measurements with the secondary radio link during a suspension of the connection with the source master node; means for suspending the connection between the user equipment (UE) and the source master node; and means for activating dual active protocol stack operation for data transmission at the user equipment (UE) with the secondary radio link and a target radio link to the target master node.

54. The apparatus according to claim 53, wherein the message comprises radio resources control (RRC) configuration signaling.

55. The apparatus according to claims 53 or 54, wherein the message comprises one or more parameters related to at least one of: a source radio condition threshold, of the master radio link, for starting the handover, use of a radio condition difference to adjust secondary radio link management (RLM), or a timer to complete the dual active protocol stack operation for a secondary cell group (SCG).

56. The apparatus according to one or more of claims 53-55, further comprising: means for receiving, from the target master node, a message associated with releasing the source master node.

57. The apparatus according to claim 56, further comprising: means for deactivating the dual active protocol stack operation based on the message associated with releasing the serving master node.

58. The apparatus according to claim 56, wherein the message associated with releasing the source master node comprises radio resource control (RRC) reconfiguration signaling.

59. The apparatus according to one or more of claims 53-58, further comprising: means for performing, based on activating the dual active protocol stack operation, a packet data convergence protocol (PDCP)-dual active protocol stack uplink transmission to the target master node on a first uplink grant.

60. The apparatus according to one or more of claims 53-59, further comprising: means for performing, based on activating the dual active protocol stack operation, a random access channel (RACH) procedure; and means for completing the handover based on performing the random access channel (RACH) procedure.

61. The apparatus according to one or more of claims 53-60, further comprising: means for checking a status of the master radio link relative to a threshold based on receiving the message.

62. The apparatus according to claim 61, wherein the suspending or the activating is based on the status of the master radio link satisfying the threshold.

63. The apparatus according to claim 62, further comprising: means for adjusting the radio link measurements for the secondary radio link based on a source radio condition offset indicated in the message.

64. The apparatus according to claim 63, further comprising: based on expiration of a timer: means for terminating the handover, or means for resuming master cell group (MCG) monitoring.

65. An apparatus, comprising: for a handover from a source master node to a target master node in dual connectivity, wherein a user equipment (UE) has a connection with a master radio link to the source master node and a secondary radio link to a source secondary node: means for transmitting, by the source master node to the user equipment (UE), a message, wherein the message is associated with triggering radio link measurements with the secondary radio link during a suspension of the connection with the source master node; and means for suspending the connection between the user equipment (UE) and the source master node.

66. The apparatus according to claim 65, wherein the message comprises radio resources control (RRC) configuration signaling.

67. The apparatus according to claims 65 or 66, wherein the message comprises one or more parameters related to at least one of: a source radio condition threshold, of the master radio link, for starting the handover, use of a radio condition difference to adjust secondary radio link management (RLM), or a timer to complete the dual active protocol stack operation for a secondary cell group (SCG).

68. The apparatus according to one or more of claims 65-67, wherein operations of the source master node associated with a dual active protocol stack are distributed between the source master node and the source secondary node.

69. The apparatus according to one or more of claims 65-68, further comprising: means for transmitting, to the source secondary node, an indication that the user equipment (UE) is to activate a dual active protocol stack operation, wherein the indication is associated with causing the source secondary node to start forwarding one or more packets to the target master node and to continue scheduling via the source master node while suspending a transmission via the source secondary node.

70. The apparatus according to one or more of claims 65-69, further comprising: means for transmitting, to the UE, an indication associated with causing the dual active protocol stack (DAPS) operation to be activated, or means for transmitting, to the UE, another indication associated with causing the dual active protocol stack (DAPS) operation to be deactivated.

71. An apparatus, comprising: for a handover from a source secondary node to a target secondary node in dual connectivity, wherein a user equipment (UE) has a connection with a master radio link to a source master node and a secondary radio link to the source secondary node: means for receiving, from the source master node, a message that indicates that the handover is to be performed; means for suspending the connection between the user equipment (UE) and the source master node; and means for activating dual active protocol stack operation for data transmission at the user equipment (UE) with the secondary radio link and a target radio link to the target secondary node.

72. The apparatus according to claim 71, wherein the message comprises radio resources control (RRC) configuration signaling.

73. The apparatus according to claims 71 or 72, wherein the message comprises one or more parameters related to at least one of: a source radio condition threshold, of the master radio link, for starting the handover, use of a radio condition difference to adjust secondary radio link management (RLM), or a timer to complete the dual active protocol stack operation for a secondary cell group (SCG).

74. The apparatus according to one or more of claims 71-73, further comprising means for receiving, from the target secondary node, a message associated with releasing the source secondary node.

75. The apparatus according to claim 74, further comprising: means for deactivating the dual active protocol stack operation based on the message associated with releasing the source secondary node.

76. The apparatus according to claim 74, wherein the message associated with releasing the source secondary node comprises radio resource control (RRC) reconfiguration signaling.

77. The apparatus according to one or more of claims 71-76, wherein the suspending or the activating is based on a status of the master radio link satisfying a threshold.

78. The apparatus according to one or more of claims 71-77, further comprising: based on expiration of a timer: means for terminating the handover, or means for resuming master cell group (MCG) monitoring.

79. A non-transitory computer readable medium comprising program instructions stored thereon for causing an apparatus to perform the methods according to any of claims 1-18 or 45-52.