WO2022028920A1

WO2022028920A1 - Conditional handover with dual connectivity

Info

Publication number: WO2022028920A1
Application number: PCT/EP2021/070624
Authority: WO
Inventors: Srinivasan Selvaganapathy; Amaanat ALI; Ahmad AWADA; Elena Virtej
Original assignee: Nokia Technologies Oy
Priority date: 2020-08-06
Filing date: 2021-07-23
Publication date: 2022-02-10
Also published as: EP4193668A1

Abstract

An apparatus comprising means for: receiving configuration information comprising at least a handover execution condition for a primary cell; multiple addition conditions for multiple primary secondary cells for dual connectivity with the primary cell, wherein the addition conditions comprise at least: an addition condition for a first one of multiple primary secondary cells for dual connectivity with the primary cell; and an addition condition for a second one of multiple primary secondary cells for dual connectivity with the primary cell; and enabling conditional handover with dual connectivity using the configuration information.

Description

TITLE

Conditional handover with dual connectivity

TECHNOLOGICAL FIELD

Embodiments of the present disclosure relate to conditional handover with dual connectivity. Some relate to a variation of 3GPP specifications to enable conditional handover with dual connectivity.

BACKGROUND

Conditional Handover (CHO) is a handover procedure that is triggered by the UE only when the configured execution condition(s) are met for a candidate primary cell (PCell). CHO only supports measurement object(s) for a target PCell as a condition for execution of CHO.

In 3GPP, Dual Connectivity (DC) is when a user equipment (UE) has contemporaneous connection to an master node (MN) (or master cell group (MCG)) and a secondary node(SN) (or secondary cell group (SCG)). Conditional handover execution with dual connectivity (DC) only supports blind access to a secondary node (SN) (or secondary cell group (SCG)).

BRIEF SUMMARY

According to various, but not necessarily all, embodiments there is provided an apparatus comprising means for: receiving configuration information comprising at least a handover execution condition for a primary cell; multiple addition conditions for multiple primary secondary cells for dual connectivity with the primary cell, wherein the addition conditions comprise at least: an addition condition for a first one of multiple primary secondary cells for dual connectivity with the primary cell; and an addition condition for a second one of multiple primary secondary cells for dual connectivity with the primary cell; and enabling conditional handover with dual connectivity using the configuration information.

In some but not necessarily all examples, the apparatus comprises means for: performing a measurement for a handover execution condition for a primary cell; and performing separate measurements for the multiple addition conditions for the multiple primary secondary cells for dual connectivity with the primary cell.

In some but not necessarily all examples, the apparatus comprises means for selecting one of the multiple primary secondary cells for conditional handover with dual connectivity, at least partially based on the the handover execution condition; the multiple addition conditions; and the multiple measurements.

In some but not necessarily all examples, the apparatus comprises means for selecting one of the multiple primary secondary cells for conditional handover with dual connectivity, at least partially based on a further condition.

In some but not necessarily all examples, the apparatus comprises means for informing a network of the selection.

In some but not necessarily all examples, the apparatus comprises means for determining if the handover execution condition for the primary cell is met and for determining if the addition condition for only one of multiple primary secondary cells is met, and means for enabling completion of conditional handover with dual connectivity to the primary cell and the one of multiple primary secondary cells if the handover execution condition for the primary cell is met and the addition condition for the only one of multiple primary secondary cells is met.

In some but not necessarily all examples, the apparatus comprises means for enabling completion of conditional handover without dual connectivity to the primary cell and enabling initiation, but not completion, of handover with dual connectivity to a selected primary secondary cell.

In some but not necessarily all examples, the configuration information comprises: configuration information for handover to the primary cell configuration information for dual connectivity to any of the multiple primary secondary cells. According to various, but not necessarily all, embodiments there is provided a method comprising: receiving configuration information comprising at least: a handover execution condition for a primary cell; multiple addition conditions for multiple primary secondary cells for dual connectivity with the primary cell, wherein the addition conditions comprise at least: an addition condition for a first one of multiple primary secondary cells for dual connectivity with the primary cell; and an addition condition for a second one of multiple primary secondary cells for dual connectivity with the primary cell; and enabling conditional handover with dual connectivity using the configuration information.

According to various, but not necessarily all, embodiments there is provided a computer program that when run a terminal node causes: storing received configuration information defining at least: a handover execution condition for a primary cell; multiple addition conditions for multiple primary secondary cells for dual connectivity with the primary cell, wherein the addition conditions comprise at least: an addition condition for a first one of multiple primary secondary cells for dual connectivity with the primary cell; and an addition condition for a second one of multiple primary secondary cells for dual connectivity with the primary cell; and enabling conditional handover with dual connectivity using the configuration information.

According to various, but not necessarily all, embodiments there is provided an apparatus comprising means for: transmitting configuration information, the configuration information comprising at least: a handover execution condition for a primary cell; multiple addition conditions for multiple primary secondary cells for dual connectivity with the primary cell, wherein the multiple addition conditions comprise at least: an addition condition for a first one of multiple primary secondary cells for dual connectivity with the primary cell; and an addition condition for a second one of multiple primary secondary cells for dual connectivity with the primary cell; enabling conditional handover with dual connectivity using the configuration information. In some but not necessarily all examples, the apparatus is configured to operate as a serving master node, transmitting configuration information to a user equipment.

In some but not necessarily all examples, the apparatus is configured to operate as a candidate serving master node, transmitting configuration information to a serving master node for onward transmission to the user equipment.

According to various, but not necessarily all, embodiments there is provided a method comprising: transmitting configuration information, the configuration information comprising at least: a handover execution condition for a primary cell; multiple addition conditions for multiple primary secondary cells for dual connectivity with the primary cell, wherein the multiple addition conditions comprise at least: an addition condition for a first one of multiple primary secondary cells for dual connectivity with the primary cell; and an addition condition for a second one of multiple primary secondary cells for dual connectivity with the primary cell; enabling conditional handover with dual connectivity using the configuration information.

According to various, but not necessarily all, embodiments there is provided a computer program that when run by a network node causes: transmitting configuration information, the configuration information defining at least: a handover execution condition for a primary cell; multiple addition conditions for multiple primary secondary cells for dual connectivity with the primary cell, wherein the multiple addition conditions comprise at least: an addition condition for a first one of multiple primary secondary cells for dual connectivity with the primary cell; and an addition condition for a second one of multiple primary secondary cells for dual connectivity with the primary cell; enabling conditional handover with dual connectivity based on the configuration information.

According to various, but not necessarily all, embodiments there is provided examples as claimed in the appended claims.

BRIEF DESCRIPTION Some examples will now be described with reference to the accompanying drawings in which:

FIG. 1 shows an example of the subject matter described herein;

FIG. 2A shows another example of the subject matter described herein;

FIG. 2B shows another example of the subject matter described herein;

FIG. 3 shows another example of the subject matter described herein;

FIG. 4A shows another example of the subject matter described herein;

FIG. 4B shows another example of the subject matter described herein;

FIG. 5 shows another example of the subject matter described herein;

FIG. 6A shows another example of the subject matter described herein;

FIG. 6B shows another example of the subject matter described herein;

FIG. 7 shows another example of the subject matter described herein;

FIG. 8 shows another example of the subject matter described herein;

DEFINITIONS

Master Node (MN): Network node that provides control plane connectivity towards the core network.

Master Cell Group (MCG): Group of cells associated with the MN, includes PCell.

Secondary Node (SN): Network node that is providing additional radio resources for the UE but is not the MN.

Secondary Cell Group (SCG): Group of cells associated with the SN, includes PSCell.

PCell: the cell for uplink/downlink connection to MN. Cell of MCG used to initiate initial access to the MN.

PSCell: the cell for uplink/downlink connection to SN. Cell of SCG used to initiate initial access to the SN.

Conditional Handover (CHO) - a handover procedure that is triggered by the UE only when the configured execution condition(s) are met for a candidate cell. Condition(s) preconfigured by network. In 3GPP, a conditional handover execution condition is specified by condExecutionCond within a CondReconfigToAddModList information element within a ConditionalReconfiguration information element within a RRCReconfiguration message. Dual Connectivity (DC): UE has contemporaneous connection to an MN and an SN. This is a mode of operation of a UE in RRC_CONNECTED, configured with a Master Cell Group and a Secondary Cell Group.

Configuration Information: Configuration Information is information used to configure operation of a UE. In 3GPP, the configuration information can, for example, be provided in an RRCReconfiguration message.

The term “configuration information comprising” an entity (e.g. handover execution condition for a primary cell; addition conditions for dual connectivity with the primary cell, etc) can mean that the configuration comprises information sufficient to obtain the entity. It may or may not comprises all parameters of the entity, it may instead comprise pointer to the entity or parameters of the entity or can mean that configuration information includes the entity.

Conditional handover (CHO) configuration information: Configuration information for handover to a primary cell. The CHO configuration information can comprise a handover execution condition for a primary cell and a measurement configuration for configuring measurements for the handover execution condition for the primary cell. Triggering conditional handover to the primary cell is dependent upon the measurements meeting the handover execution condition for the primary cell.

In 3GPP, a RRCReconfiguration message specifies a ConditionalReconfiguration information element which provides the CHO configuration. The ConditionalReconfiguration information element comprises a CondReconfigToAddModList information element. The CondReconfigToAddModList information element comprises condExecutionCond and condRRCReconfig. Handover execution condition(s) for a primary cell are specified by condExecutionCond. The RRCReconfiguration message to be applied when the specified conditions are met is provided by condRRCReconfig.

Dual Connectivity (DC) configuration information: Configuration information for dual connectivity to a primary secondary cell. The DC configuration information can comprises an addition condition for a primary secondary cell for dual connectivity with the primary cell and a measurement configuration for configuring measurements for an addition condition for the primary secondary cell for dual connectivity with the primary cell i.e. dual connectivity of the UE with both the primary cell and the primary secondary cell. Triggering addition of a primary secondary cell for dual connectivity is dependent upon the measurements meeting the addition condition for the primary secondary cell.

In 3GPP, a RRCReconfiguration message specifies a ConditionalReconfiguration information element which provides addition conditions for the DC. The ConditionalReconfiguration information element comprises a CondReconfigToAddModList information element. The CondReconfigToAddModList information element comprises condExecutionCond and condRRCReconfig. Addition condition(s) for a primary secondary cell (PSCell) are specified by condExecutionCond. The RRCReconfiguration message to be applied when the specified conditions are met is provided by condRRCReconfig.

Dual connectivity at conditional handover can be abbreviated to DC-CHO e.g. DC-CHO configuration means a configuration for a dual connectivity at conditional handover. An important new aspect of some examples is that multiple DC-CHO configurations are provided to provide multiple options for a dual connectivity at conditional handover to a particular PCell/MN/MCG. The collection of multiple DC-CHO configurations can be abbreviated to a M-DC-CHO configuration. M-DC-CHO can therefore define a class comprising only multiple (M) instances of dual connectivity at conditional handover DC-CHO for the same PCell/MN/MCG.

DETAILED DESCRIPTION

FIG 1 illustrates an example of a network 100 comprising a plurality of network nodes including terminal nodes 110, access nodes 120 and one or more core nodes 129. The terminal nodes 110 and access nodes 120 communicate with each other. The one or more core nodes 129 communicate with the access nodes 120.

The network 100 is in this example a radio telecommunications network, in which at least some of the terminal nodes 110 and access nodes 120 communicate with each other using transmission/reception of radio waves/signals.

The one or more core nodes 129 may, in some examples, communicate with each other. The one or more access nodes 120 may, in some examples, communicate with each other. The network 100 may be a cellular network comprising a plurality of cells 122 each served by an access node 120. In this example, the interface between the terminal nodes 110 and an access node 120 defining a cell 122 is a wireless interface 124.

The access node 120 is a cellular radio transceiver. The terminal nodes 110 are cellular radio transceivers.

In the example illustrated the cellular network 100 is a third generation Partnership Project (3GPP) network in which the terminal nodes 110 are user equipment (UE) and the access nodes 120 are base stations.

In the particular example illustrated the network 100 is an Evolved Universal Terrestrial Radio Access network (E-UTRAN). The E-UTRAN consists of E-UTRAN NodeBs (eNBs) 120, providing the E-UTRA user plane and control plane (e.g. RRC) protocol terminations towards the UE 110. The eNBs 120 are interconnected with each other by means of an X2 interface 126. The eNBs are also connected by means of the S1 interface 128 to the Mobility Management Entity (MME) 129.

In other example the network 100 is a Next Generation (or New Radio, NR) Radio Access network (NG-RAN). The NG-RAN consists of gNodeBs (gNBs) 120, providing the user plane and control plane (e.g. RRC) protocol terminations towards the UE 110. The gNBs 120 are interconnected with each other by means of an X2/Xn interface 126. The gNBs are also connected by means of the N2 interface 128 to the Access and Mobility management Function (AMF).

In examples, the network 100 can comprise a combination of E-UTRAN and NG-RAN.

A UE can perform a handover procedure to change the serving cell of the UE. In examples, a handover procedure can be a conditional handover procedure.

A conditional handover (CHO) procedure can be considered a handover that is triggered by the UE when one or more handover execution conditions are met. The handover execution conditions can be pre-configured by the network 100.

In examples, the UE 110 starts evaluating the execution condition(s) for CHO candidate primary cells upon receiving a CHO configuration, and executes the handover command once the execution condition(s) are met for a CHO candidate primary cell. The UE may stop evaluating the execution condition(s) for other candidate primary cells once the execution condition(s) are met.

In examples, a UE can be provided with additional radio resources using dual connectivity (DC).

In DC, the configured set of serving cells for a UE has two subsets: the Master Cell Group (MCG) containing the serving cells of a Master Node (MN), and the Secondary Cell Group (SCG) containing the serving cells of a Secondary Node (SN).

In examples, the MN can be considered to be a network node that provides control plane connectivity towards the core network and the SN can be considered to be a network node that is providing additional radio resources for the UE but is not the MN.

The MCG comprises a Primary Cell (PCell) for uplink/downlink connection to the MN. In examples, the PCell is the cell of the MCG used to initiate initial access to the MN by the UE.

Similarly, the SCG comprises a Primary Secondary Cell (PSCell) for uplink/downlink connection to the SN. In examples, the PSCell is the cell of the SCG used to initiate initial access to the SN by the UE. The PSCell can be configured with Physical Uplink Control Channel (PUCCH) resources.

In 3GPP, a RRCReconfiguration message specifies, for the MCG, a MCG configuration via CellGroupConfig and a measurement configuration via measConfig and specifies, for each SCG, a SCG configuration via CellGroupConfig and a measurement configuration via measConfig. The RRCReconfiguration message can also provide a ConditionalReconfiguration information element which provides addition conditions for the DC. The ConditionalReconfiguration information element comprises a CondReconfigToAddModList information element. The CondReconfigToAddModList information element comprises condExecutionCond and condRRCReconfig. Addition condition(s) for a primary secondary cell (PSCell) are specified by condExecutionCond. The RRCReconfiguration message to be applied when the specified conditions are met is provided by condRRCReconfig.

It is desirable to enable a conditional handover with dual connectivity. A conditional handover with dual connectivity changes the MN (and optionally the SN) of a DC configuration. Such a handover is an inter-MN handover.

During DC, SN terminated SCG bearers terminate in the SN and MN terminated SCG bearers terminate in the MN. They are end to end tunnels terminating at the Packet Data Convergence Protocol (PDCP) layer. In examples, an SCG Bearer can be a user plane bearer with the PDCP either at the MN or the SN but will always use the Radio Link Control (RLC), Medium Access Control (MAC) and Physical layers within the SN.

MN terminated MCG bearers terminate in the MN and SN terminated MCG bearers terminate in the SN. They are end to end tunnels terminating at the Packet Data Convergence Protocol (PDCP) layer. In examples, an MCG Bearer can be a user plane bearer with the PDCP either at the MN or the SN but will always use the Radio Link Control (RLC), Medium Access Control (MAC) and Physical layers within the MN.

In examples, a traffic stream can be remapped from an SCG bearer to an MCG bearer (and vice versa) using RRCReconfiguration.

As bearers are at a higher layer than the physical layer (layer 1) they can be prepared independently to the physical layer connection or lower sub-layer (e.g. Radio Link Control (RLC) or Medium Access Control (MAC)) connection.

A physical layer connection between a UE and a network node can be suspended. In a suspended state a UE and the network is configured to maintain resources at higher layers so that, for example, a user plane connection can be quickly resumed when the physical layer connection resumes. In a suspended state, the mapping of the bearers may be maintained in anticipation of a resumption of the physical connection.

From the UE perspective, the completion of conditional handover with dual connectivity, requires a completion of conditional handover to a new primary cell and a completion of addition of a primary secondary cell for dual connectivity.

From the network perspective, the completion of conditional handover with dual connectivity, requires a completion of conditional handover to a new serving MN and a completion of addition of a SN for dual connectivity.

In some examples, when performing conditional handover with dual connectivity, the completion of conditional handover to the primary cell/MN is contemporaneous with a completion of addition of a primary secondary cell/SN.

In some examples, when performing conditional handover with dual connectivity, the initiation e.g. triggering/execution of conditional handover to the primary cell/MN is contemporaneous with a completion of addition of a primary secondary cell/SN.

In some examples, when performing conditional handover with dual connectivity, the completion of conditional handover to the primary cell/MN occurs before the completion of addition of a primary secondary cell/SN. The completion of addition of a primary secondary cell/SN is delayed. This can be described as delayed access.

In some examples, when performing conditional handover with dual connectivity, the initiation e.g. triggering/execution of conditional handover to the primary cell/MN occurs before the initiation e.g. triggering/execution of addition of a primary secondary cell/SN. The initiation of addition of a primary secondary cell/SN is delayed. This can be described as delayed access.

The completion of conditional handover to the primary cell/MN can, for example, result in direct access of the UE to a new MN; establishment of a radio link between the UE and the MN/MCG that enables the transfer of data via uplink (UL) and/or downlink (DL). The radio link can, for example, be established by initiating a RACH procedure at the UE; traffic flow using bearer between the UE and the network via the MN/MCG. The completion of addition of the primary secondary cell/SN can, for example, result in direct access of the UE to a new SN; establishment of a radio link between the UE and the SN/SCG that enables the transfer of data via uplink (UL) and/or downlink (DL). The radio link can, for example, be established by initiating a RACH procedure at the UE; traffic flow using a bearer between the UE and the network via the SN/SCG.

FIG 2 illustrates an example of a method 200. The method 200 can, for example, be performed by a terminal node 110 such as user equipment. The method enables conditional handover to a primary cell while supporting dual connectivity with multiple primary secondary cells.

The method 200, at block 202, comprises receiving configuration information 10 comprising at least: a handover execution condition 22 for a primary cell; and multiple addition conditions 32 for multiple primary secondary cells for dual connectivity with the primary cell, wherein the multiple addition conditions 32 comprise at least: an addition condition 32 for a first one of multiple primary secondary cells for dual connectivity with the primary cell; and an addition condition 32 for a second one of multiple primary secondary cells for dual connectivity with the primary cell; and

The method 200, at block 204, comprises enabling conditional handover with dual connectivity using the configuration information 10.

At block 204 triggering completion of CHO to the primary cell is dependent upon meeting the handover execution condition 22 for the primary cell. Also at block 204, triggering completion of addition of a primary secondary cell for dual connectivity can be dependent upon meeting the addition condition 32 for that primary secondary cell.

FIG 2B illustrates an example of block 204. In this example, enabling conditional handover (CHO) with dual connectivity using the configuration information comprises: at block 212, by the UE, performing a measurement for the handover execution condition 22 for the primary cell, based on the measurement configuration 24; at block 214, performing separate measurements for the multiple addition conditions 32 for the multiple primary secondary cells for dual connectivity with the primary cell, based on the addition measurement configurations 34; at block 216, selecting one of the multiple primary secondary cells for conditional handover with dual connectivity, at least partially based on the handover execution condition 22, the multiple addition conditions 32, and the multiple measurements for at least addition conditions; at block 218, the UE informs the network of the selection.

Triggering completion of CHO to the primary cell is dependent upon meeting the handover execution condition 22 for the primary cell. It can, for example, be dependent upon the measurement for the handover execution condition 22 for the primary cell and the handover execution condition 22 for the primary cell.

Triggering completion of addition of a primary secondary cell for dual connectivity can be dependent upon triggering completion of CHO to the primary cell and meeting the addition condition 32 for that primary secondary cell.

FIG 3 illustrates an example of a method 220. The method 220 can, for example, be performed by a network node 220 such as a base station e.g. gNB. The method 220 enables conditional handover to a primary cell while supporting dual connectivity with multiple primary secondary cells.

The method 220, at block 222, comprises transmitting configuration information 10, the configuration information 10 comprising at least: a handover execution condition 22 for a primary cell; and multiple addition conditions 32 for multiple primary secondary cells for dual connectivity with the primary cell, wherein the multiple addition conditions 32 comprise at least: an addition condition 32 for a first one of multiple primary secondary cells for dual connectivity with the primary cell; and an addition condition 32 for a second one of multiple primary secondary cells for dual connectivity with the primary cell;

The method 220, at block 224, comprises enabling a conditional handover with dual connectivity based on the configuration information 10 (e.g., CHO config). In some examples, the method 220 is performed by a candidate serving master node (i.e. , a Target MN), transmitting configuration information 10 to a serving master node (i.e., a Source MN) for onward (or, transparent) transmission to the user equipment 110.

In some example, the method 220 is performed by a serving master node (a Target MN), directly transmitting configuration information 10 to the user equipment 110.

The configuration information 10 can be prepared at the Target MN 120T in response to the Source MN 120s sending a handover request message to the Target MN 120T.

Completion of conditional handover with dual connectivity requires completion of conditional handover to the primary cell and completion of addition of one of the primary secondary cells for dual connectivity.

Completion, with respect to a network node or cell group, means direct access of the UE to the node. There is establishment of a radio link between the UE and the node/cell group that enables the transfer of data via uplink (UL) and/or downlink (DL). The radio link can, for example, be established using a RACH procedure at the UE. There is, for example, traffic flow using a bearer between the UE and the network via the node/cell group.

The completion of conditional handover to the primary cell can require at least meeting (satisfaction of) the handover execution condition 22 for the primary cell. In some examples, the meeting (satisfaction of) the handover execution condition 22 for the primary cell can require meeting (satisfaction of) a handover execution condition 22 associated with one or more measurements for the primary cell.

The completion of addition of one member of the set of primary secondary cells for dual connectivity with the primary cell can require at least meeting (satisfaction of) one of the multiple addition conditions 32 for multiple primary secondary cells for dual connectivity with the primary cell. In some examples, the meeting (satisfaction of) the addition condition 32 for a particular primary secondary cell for dual connectivity with the primary cell can, for example, require meeting (satisfaction of) an addition condition 32 associated with one or more measurements for the particular primary secondary cell. The one or more measurements can, for example, be the same for all primary secondary cells or can be specified separately for each primary secondary cell. The addition condition 32 associated with the one or more measurements can, for example, be the same for all primary secondary cells or can be specified separately for each primary secondary cell.

The completion of addition of one member of the set of primary secondary cells for dual connectivity with the primary cell can also require at least meeting (satisfaction of) a primary cell condition associated with the primary cell. In some examples, this requires meeting (satisfaction of) a primary cell condition associated with one or more measurements for the primary cell. The same primary cell condition can be shared by the set of multiple addition conditions 32 for the set of multiple primary secondary cells for dual connectivity with the primary cell. In some examples, the same shared primary cell condition is the handover execution condition 22 for that primary cell. In these examples, meeting (satisfaction of) the primary cell condition (the handover execution condition 22 for the primary cell) requires meeting (satisfaction of) a handover execution condition 22 associated with one or more measurements for the primary cell

Thus, in at least some examples, completion of addition of a first primary secondary cell in a set of primary secondary cells for dual connectivity with the primary cell requires meeting (satisfaction of) the primary cell condition (e.g. the handover execution condition 22 for the primary cell). The primary cell condition (e.g. the handover execution condition 22 for the primary cell) being associated with one or more measurements (e.g. handover measurements) for the primary cell. It also requires meeting (satisfaction of) the addition condition 32 for the first primary secondary cell for dual connectivity with the primary cell. The addition condition 32 being associated with one or more addition measurements for the first primary secondary cell. The completion of addition of a second primary secondary cell in the set of primary secondary cells for dual connectivity with the primary cell requires meeting (satisfaction of) the primary cell condition (e.g. the handover execution condition 22 for the primary cell). The primary cell condition (e.g. the handover execution condition 22 for the primary cell) being associated with one or more measurements (e.g. handover measurements) for the primary cell. It also requires meeting (satisfaction of) the addition condition 32 for the second primary secondary cell for dual connectivity with the primary cell. The addition condition 32 being associated with one or more addition measurements for the second primary secondary cell.

Thus, in these examples, completion of addition of a particular primary secondary cell in the set of primary secondary cells for dual connectivity with the primary cell requires the same condition and measurement for the primary cell (e.g. those required for conditional handover) and a potentially individually specified addition condition 32 and potentially individually specified addition measurement for the particular primary secondary cell. It is also possible for an addition condition 32 to be shared between different primary secondary cells in the set. It is also possible for an addition measurement to be shared between different primary secondary cells in the set.

Configuration information 10 can therefore comprise a handover execution condition 22 for a primary cell by, for example, defining an association between a handover execution condition 22 and a primary cell. The configuration information can define the association by using an identifier for a handover execution condition 22 and using an identifier of the primary cell. The configuration information 10 can itself comprise the execution condition, or it can be defined separately. The configuration information 10 can also comprise a measurement configuration 24 for configuring a handover measurement for the handover execution condition 22 for the primary cell by defining an association between the handover execution condition 22 and a particular measurement configuration.

The configuration information 10 can comprise an addition condition 32 for a primary secondary cell for dual connectivity with the primary cell, for example, defining an association between an addition condition 32 and a primary secondary cell. The configuration information can define the association by using an identifier for an addition condition 32 and using an identifier of the primary secondary cell. The configuration information 10 can itself comprise the addition condition 32, or it can be defined separately. Configuration information 10 can comprise a measurement configuration 34 for configuring an addition measurement for the addition condition 32 for the primary secondary cell by defining an association between the addition condition 32 and a particular measurement configuration 34.

FIG 4A schematically illustrates an example of configuration information 10. In this example, the set of multiple primary secondary cells include at least a first primary secondary cell and a second primary secondary cell.

The configuration information 10 comprises: a) a conditional handover configuration 20 comprising: i) a handover execution condition 22 for a primary cell; and ii) a handover measurement configuration 24 for the handover execution condition 22; b) a first dual connectivity at conditional handover (DC-CHO) configuration 30i comprising: i) a first addition condition 32i for a first primary secondary cell for dual connectivity with the primary cell; ii) a first measurement configuration 34i for the first addition condition 32i; c) a second dual connectivity at conditional handover (DC-CHO) configuration 302 comprising: i) a second addition condition 322 for a second primary secondary cell of the set for dual connectivity with the primary cell; ii) a second measurement configuration 342 for the second addition condition 322.

The configuration information 10 can comprise: another dual connectivity at conditional handover (DC-CHO) configuration 30; comprising another addition condition 32; for another primary secondary cell of the set for dual connectivity with the primary cell; and another measurement configuration 34; for another addition condition 32j.

The multiple dual connectivity at conditional handover (DC-CHO) configurations 30 provide multiple dual connectivity at conditional handover configurations M-DC-CHO. It comprises multiple addition conditions 32 for the set of multiple primary secondary cells for dual connectivity with the same primary cell, and multiple measurement configurations 34 for respective addition conditions 32.

Multiple {MN, SNn} configuration pairs can be defined, where each pair shares the same CHO config 20 and has a different DC-CHO config 30_n.

The configuration information 10 can additionally comprise configuration information for handover to the primary cell; and configuration information for dual connectivity to any of the multiple primary secondary cells.

FIG 4B schematically illustrates an example of configuration information 10 in a format usable for 3GPP. In this example, the set of multiple primary secondary cells include at least a first primary secondary cell and a second primary secondary cell. All the configuration information 10 is provided, in this example, in a single RRCReconfiguration message. A measConfig information element associates, in pairs, a MeasID and a MeasObjectID. The MeasID is an identifier of a measurement configuration used, for example, to define a measurement configuration 24, 34 required in a handover execution condition 22 or an addition condition 32. The MeasObjectID is an identifier of a specific measurement configuration 23, 34. For example, one MeasObjectID could specify measurement of RSRP and another could specify measurement of RSSI. It is possible for a specific measurement configuration to be re-used in different association pairs.

The measConfig defines a handover measurement configuration 24 for the handover execution condition 22. The measConfig defines one or more handover measurement configurations 34 for the respective multiple addition conditions 32.

There is a CondExecutionCond information element that defines, a handover execution condition 22 for a primary cell using one or two MeasID.

There is one or more CondExecutionCond information elements that define(s), an addition condition 32 for each primary secondary cell of the set for dual connectivity with the primary cell. In one example, there is a CondExecutionCond information element that defines, a first addition condition 32 for a first primary secondary cell of the set for dual connectivity with the primary cell and there is a CondExecutionCond information element that defines, a second addition condition 32 for a second primary secondary cell of the set for dual connectivity with the same primary cell.

Examples can therefore extend CondExecutionCond. In some examples, there can be a distinct CondExecutionCond information element for the primary cell and each of the primary secondary cells. In other examples, there can be a distinct CondExecutionCond information element for the primary cell and a distinct CondExecutionCond that defines all the addition conditions 32 of the set of primary secondary cells for DC with the primary cell. In other examples, there is a single CondExecutionCond information element that defines all the conditional handover execution condition 22 of the primary cell and also the addition conditions 32 of the set.

The configuration information 10 comprises: configuration information for handover to the primary cell e.g. CellGroupConfig in masterCellGroup information element; and comprises configuration information for dual connectivity to any of the multiple primary secondary cells e.g. CellGroupConfigs in secondaryCellGroup information element.

In some examples (single-stage), initiation of addition of a second primary cell in the set of primary secondary cells for dual connectivity with the primary cell is also completion of addition of a second primary cell in the set of primary secondary cells for dual connectivity with the primary cell.

In other examples (dual-stage), initiation of addition of a second primary cell in the set of primary secondary cells for dual connectivity with the primary cell is distinct from completion of addition of a second primary cell in the set of primary secondary cells for dual connectivity with the primary cell.

For a single-stage implementation, initiation/completion of addition of a primary secondary cell in the set of primary secondary cells for dual connectivity with the primary cell requires: i) meeting (satisfaction of) the primary cell condition (e.g. the handover execution condition 22 for the primary cell). The primary cell condition (e.g. the handover execution condition 22 for the primary cell) being associated with one or more measurements (e.g. handover measurements) for the primary cell; and ii) meeting (satisfaction of) the addition condition 32 for the primary secondary cell for dual connectivity with the primary cell. The addition condition 32 being associated with one or more addition measurements for the second primary secondary cell.

For a multi-stage implementation, a) initiation of addition of a second primary secondary cell in the set of primary secondary cells for dual connectivity with the primary cell requires: meeting (satisfaction of) the primary cell condition (e.g. the handover execution condition 22 for the primary cell). The primary cell condition (e.g. the handover execution condition 22 for the primary cell) being associated with one or more measurements (e.g. handover measurements) for the primary cell; and b) completion of addition of a second primary secondary cell in the set of primary secondary cells for dual connectivity with the primary cell requires meeting (satisfaction of) the addition condition 32 for the second primary secondary cell for dual connectivity with the primary cell. The addition condition 32 being associated with one or more addition measurements for the second primary secondary cell. The UE 110 is therefore able to complete conditional handover without dual connectivity to the primary cell and enable initiation, but not completion, of handover with dual connectivity to a selected primary secondary cell.

In this example a bearer for a selected primary secondary cell can be prepared in response to initiation of addition of a primary secondary cell but no access to the bearer via PCell or PSCell is allowed until completion of addition of the primary secondary cell.

After initiation, but before completion, of the addition of the of the primary secondary cell, the physical layer connection between the UE 110 and the primary secondary cell is suspended. In a suspended state, a UE and the network are configured to maintain resources at higher layers so that, for example, a user plane connection can be quickly resumed when the physical layer connection resumes. In a suspended state, the mapping of the bearers may be maintained in anticipation of a resumption of the physical connection. On completion of the addition of the of the primary secondary cell, the suspension state is stopped and a physical connection is resumed.

The UE 110, after initiation of addition of a second primary secondary cell continues to determine satisfaction of the respective addition condition.

It will therefore be appreciated that, in at least some examples, the UE 110 determines if the handover execution condition 22 for the primary cell is met and determines if the addition condition 32 for only one of multiple primary secondary cells is met, and enables completion of conditional handover with dual connectivity to the primary cell and the one of multiple primary secondary cells if the handover execution condition 22 for the primary cell is met and the addition condition 32 for only one of multiple primary secondary cells is met.

In some examples, addition conditions 32 for more than one of the multiple primary secondary cells is met. Thus the primary cell condition (e.g. the handover execution condition 22 for the primary cell) is met. The primary cell condition (e.g. the handover execution condition 22 for the primary cell) being associated with one or more measurements (e.g. handover measurements) for the primary cell. However, multiple addition conditions 32 for the set of primary secondary cells for dual connectivity with the primary cell are met. The addition conditions 32 being associated with one or more addition measurements for the respective primary secondary cell. A further contention resolution condition can be used to select one primary secondary cell from those that satisfy the additions condition(s) 32.

The UE 110 can be configured to select one of the multiple primary secondary cells for conditional handover with dual connectivity, at least partially based on a further contention condition. The further contention condition can, for example, be a network informed radio condition for selection. The selected primary secondary cell may be the best available (best signal power) or a highest priority of those above a quality threshold (e.g. above a minimum power level).

In other examples, no addition conditions 32 for more than one of the multiple primary secondary cells is met. Thus the primary cell condition (e.g. the handover execution condition 22 for the primary cell) is met. The primary cell condition (e.g. the handover execution condition 22 for the primary cell) being associated with one or more measurements (e.g. handover measurements) for the primary cell. However, none of the addition conditions 32 for the set of primary secondary cells for dual connectivity with the primary cell is met. The addition conditions 32 being associated with one or more addition measurements for the respective primary secondary cell A further continuation condition can be used to select a primary secondary cell.

The UE 110 can be configured to select one of the multiple primary secondary cells for conditional handover with dual connectivity, at least partially based on a further continuation condition. The further continuation condition can, for example, be a network informed condition for selection. The further continuation condition can, for example, require expiry of a timer started when the primary cell condition 22 is met. The further continuation condition can also comprise a radio condition for selection. The selected primary secondary cell, after a timeout without meeting an addition condition 32 for one of the multiple primary secondary cells, can be the best available (best signal power) or a highest priority of those above a quality threshold (e.g. above a minimum power level). In the following description relating to FIG 5, 6A and 6B, the handover execution condition 22 for a primary cell is referred to as the PCell condition 22 and an addition condition 32 for a primary secondary cell for dual connectivity is referred to as a PSCell condition 32.

As previously described with reference to FIG 4A, a CHO configuration 20 provides at least the handover execution condition 22 for a primary cell (MCG) and a measurement configuration 24 for that condition. A DC-CHO configuration 30 provides at least the addition condition 32 for a primary secondary cell (SCG) for dual connectivity with the primary cell (MCG) and a measurement configuration 34 for that condition. A M-DC-CHO configuration provides multiple DC-CHO configurations 30 associated with different primary secondary cells (different SCGs) but the same primary cell. A CHO configuration pair can comprise a CHO configuration 20 (the handover execution condition 22 for a primary cell (MCG) and a measurement configuration 24 for that condition) and an associated DC-CHO configuration 30 (the addition condition 32 for a primary secondary cell (SCG) for dual connectivity with the primary cell (MCG) and a measurement configuration 34 for that condition).

As a precursor to the stages illustrated in FIG 5, the LIE110 can inform the Source MN of its capabilities, such as its capability to select one of multiple SN/SCG for a SN/MCG for CHO to the SN/MCG with DC with the SN/SCG i.e. it supports M-DC-CHO.

At stage 301 , a Source MN sends a Handover Request for M-DC-CHO to a Target MN. The request is for DC-CHO for multiple target SNs (SCGs). The Handover Request indicates to the Target MN that the Source MN supports M-DC-CHO. It supports reception of two or more DC-CHO configurations for multiple different SN/SCG.

When M-DC-CHO support is indicated by the Source MN to the Target MN in HO-REQ, the Target MN at stage 302, can prepare multiple DC-CHO configurations 30 with different SNs/SCGs (there can be a maximum of N such DC-CHO configurations associated with a given target MN).

The Target MN decides to prepare multiple (two in this example) SNs/SCGs for CHO with DC. The multiple Target SNs are Target SN-1 and Target SN-2.

At stage 303, the Target MN performs SCG addition procedure with Target SN-1. SN-1 provides a SCG configuration to Target MN. At stage 304, the Target MN performs SCG addition procedure with Target SN-2. SN-2 provides a SCG configuration to Target MN.

At stage 305, the Target MN includes, for transmission, multiple SCG measurement configurations 34, one for SCG-1 and one for SCG-2, in the HO REQ ACK.

In Option 1 a separate Handover Request Ack is sent from Target MN to Source MN for each Target SN/SCG. At stage 306A a Handover Request Ack is sent from Target MN to Source MN. It includes a Target MN configuration for DC with SCG-1 including a corresponding measurement configuration 34. At stage 306B, a Handover Request Ack is sent from Target MN to Source MN. It includes Target MN configuration for DC with SCG- 2 including a corresponding measurement configuration 34. This is different from preparing multiple legacy target configurations in the same node. Here the target cell-ID is the same, it is only the SCG configuration and corresponding measurement configuration that will differ. For a single HO-REQ, there will be two (or more) HO-REQ-ACK responses (one for each Target SN/SCG) with same XN-AP-ID and target-cell ID. The last HO-REQ-ACK response may contain an end marker signifying end of message (EOM).

In Option 2 (alternative to option 1) a combined Handover Request Ack is sent from Target MN to Source MN for all Target SNs/SCGs. It includes a Target MN configuration for DC with SCG-1 and SCG-2 including respective measurement configurations 34. The Target MN provides N Target MN configuration for DC with the N SNs/SCGs in a single HO-REQ- ACK message. The configurations include suggested measurement-configuration 34 for each SN/SCG.

At stage 307, the Source NM sends and UE receives configuration information 10 comprising at least: a handover execution condition 22 for a primary cell; and multiple addition conditions 32 for multiple primary secondary cells for dual connectivity with the primary cell, wherein the addition conditions 32 comprise at least: an addition condition 32 for a first one of multiple primary secondary cells for dual connectivity with the primary cell; and an addition condition 32 for a second one of multiple primary secondary cells for dual connectivity with the primary cell. The configuration information 10 can also comprise a measurement configuration 24 configuring one or more measurements for a handover execution condition 22 for a primary cell; and a measurement configuration 34, for each primary secondary cell, configuring one or more measurements for an addition condition 32 for the primary secondary cell for dual connectivity with the primary cell.

The configuration information 10, in 3GPP, can be sent using a RRC Reconfiguration message.

In 3GPP, a RRCReconfiguration message can be modified to specify not only CHO configuration 20 but also multiple DC-CHO configurations (plural) 30 associated with the CHO configuration 20 as previously described. It is possible to extend condExecutionCond (or a higher IE within RRCReconfiguration IE) to include: multiple addition conditions 32 for multiple primary secondary cells for dual connectivity with the same primary cell. condExecutionCond IE can be used to indicate 1 or 2 measID for the PCell for CHO. It could be extended to include up to 2 more MeasID (and addition condition(s) 32) for each one of multiple PSCells. Multiple measID for a PSCell supports the measurement of different reporting quantities (i.e. RSRP, RSSI, RSRQ). As an alternative to extending condRRCReconfig, the RRCReconfiguration message can instead have multiple instances of condRRCReconfig. In some examples, more than one instance of condRRCReconfig can be added to the same CHO execution condition 22 defined by condExecutionCond.

In other examples, the Source MN configures N separate DC-CHO Configuration pairs each with two measurement ID/conditions: one for PCell (MCG)- the PCell condition 22 and another for PSCell (SCG)- the PSCell condition 32. The N DC-CHO configuration pairs will have the same PCell condition 22. The PSCell condition 32 may be same or different. For each {MCG, SCG] pair (where the target MN remains the same) indicated by the condRRCReconfig then the condExecutionCond IE is extended to add up to 2 more measld to also include the PSCell.

At stage 308, the UE 110 stores the configuration information 10.

Two alternatives are illustrated in FIG 6A and FIG 6B respectively. In FIG 6A, when the PCell condition 22 is met, a first DC-CHO configuration pair Configuration-1 {MCG-1 , SCG-1} that is associated with a first PSCell/SCG and a second DC-CHO configuration pair Configuration-2 {MCG-2, SCG-2} that is associated with a second PSCell/SCG qualify for further selection.

Depending on the PSCell condition 32, Configuration-1 or Configuration-2 is selected depending on which PSCell meets the PSCell condition 32.

In case both SCGs do not meet the selection criteria of the PSCell condition 32 within a time duration (maximum delay period) started when the PCell condition 22 is met, the UE 110 proceeds to execute an RRC-Reconfiguration comprising a SCG configuration for a selected one of the SCG. The selection can be based on a further criterion that is provided by the network (e.g. radio condition that allows selection of SCG). In one example, the further criterion could be to select the SCG configuration corresponding to the PSCell having the strongest measurement when the PCell condition is met. In another example, the further criterion could be a prioritized SCG (indication of which SCG to use) in case both SCGs meet a minimum received power level that is provided as well by the network, i.e., both PSCells of SCG 1 and SCG2 have received power above a certain threshold.

One of the multiple SNs/SCGs has therefore been selected. The selected SCG is, in this example, SCG-1.

At stage 309A, the UE applies the DC-CHO configuration 30 associated with the selected SN/SCG and informs the network of the selected SN/SCG. At stage 310A, the UE 110 sends RRC Reconfiguration Complete (selected SCG: SCG-1) to Target MN. At stage 311 A the Target MN sends SgNB Reconfiguration Complete message to the SN of the selected SCG. At stage 312A the UE 110 performs random access/SCG activation (access) to the SN (SCG-1).

In FIG 6B, when the PCell condition 22 is met, the UE 110 performs CHO configuration by selecting the SCG that meets the further criterion provided by the network (explained above). The UE 110 does not delay the CHO execution until the time duration (maximum delay period) started after the PCell condition 22 is met. The UE 110 performs two-stage process- the UE applies the MCG configuration and the SCG configuration; performs access to the selected PCell/MN/MCG (completion of CHO to MN) but does not perform access to the selected PSCell/SN/SCG (no completion of DC). The UE informs the target MN about the status of the selected SCG, i.e. SCG is configured but not accessed yet (access delayed). The UE may continue with further evaluation of PSCell condition 32 for the selected PSCell after initiation of CHO with DC. Once the addition condition 32 is met, the UE performs SCG access completing CHO with DC.

Referring to FIG 6B, at stage 309B, the UE 110 applies a CHO configuration and selects a SN/SCG. The selection can in some examples be based on a further criterion e.g. power.

At stage 310B, the UE 110 informs the network of the selected SN/SCG. The UE sends RRC Reconfiguration Complete (SCG retain: SCG-1 , PSCell measurement results) to Target MN.

At stage 311B, the Target MN sends SgNB Reconfiguration Complete message (retain) to the SN of the selected SCG.

At stage 312B, the Target MN releases the non-selected SCGs/SNs.

At stage 313B, the UE 110 continues measurements of PSCell for selected SCG-1 for conditional activation for SCG-1 (conditional access).

At stage 314B, the access condition is met. The access condition can, in at least some examples, be the addition condition 32 for the selected SCG.

At stage 315B, the PSCell can be accessed.

At stage 316B the UE 110 performs random access/SCG activation (access) to the SN (SCG-1). This completes the addition.

At stage 317B, the SN (SCG-1) sends an SCG activation indication to the serving MN.

Fig 7 illustrates an example of a controller 400. The controller can be used in an apparatus such as a network node 110, 120. Implementation of a controller 400 may be as controller circuitry. The controller 400 may be implemented in hardware alone, have certain aspects in software including firmware alone or can be a combination of hardware and software (including firmware). As illustrated in Fig 7 the controller 400 may be implemented using instructions that enable hardware functionality, for example, by using executable instructions of a computer program 406 in a general-purpose or special-purpose processor 402 that may be stored on a computer readable storage medium (disk, memory etc) to be executed by such a processor 402.

The processor 402 is configured to read from and write to the memory 404. The processor 402 may also comprise an output interface via which data and/or commands are output by the processor 402 and an input interface via which data and/or commands are input to the processor 402.

The memory 404 stores a computer program 406 comprising computer program instructions (computer program code) that controls the operation of the apparatus when loaded into the processor 402. The computer program instructions, of the computer program 406, provide the logic and routines that enables the apparatus to perform the methods illustrated in Figs. The processor 402 by reading the memory 404 is able to load and execute the computer program 406.

A terminal node 110, for example user equipment or mobile equipment, can therefore comprises: at least one processor 402; and at least one memory 404 including computer program code the at least one memory 404 and the computer program code configured to, with the at least one processor 402, cause the apparatus at least to perform: receiving configuration information comprising at least a handover execution condition 22 for a primary cell; multiple addition conditions 32 for multiple primary secondary cells for dual connectivity with the primary cell, wherein the addition conditions 32 comprise at least: an addition condition 32 for a first one of multiple primary secondary cells for dual connectivity with the primary cell; and an addition condition 32 for a second one of multiple primary secondary cells for dual connectivity with the primary cell; and enabling conditional handover with dual connectivity using the configuration information.

A network node 120 can therefore comprises: at least one processor 402; and at least one memory 404 including computer program code the at least one memory 404 and the computer program code configured to, with the at least one processor 402, cause the apparatus at least to perform: transmitting configuration information, the configuration information comprising at least: a handover execution condition 22 for a primary cell; multiple addition conditions 32 for multiple primary secondary cells for dual connectivity with the primary cell, wherein the multiple addition conditions 22 comprise at least: an addition condition 32 for a first one of multiple primary secondary cells for dual connectivity with the primary cell; and an addition condition 32 for a second one of multiple primary secondary cells for dual connectivity with the primary cell; enabling conditional handover with dual connectivity using the configuration information.

As illustrated in Fig 8, the computer program 406 may arrive at the apparatus via any suitable delivery mechanism 408. The delivery mechanism 408 may be, for example, a machine readable medium, a computer-readable medium, a non-transitory computer- readable storage medium, a computer program product, a memory device, a record medium such as a Compact Disc Read-Only Memory (CD-ROM) or a Digital Versatile Disc (DVD) or a solid state memory, an article of manufacture that comprises or tangibly embodies the computer program 406. The delivery mechanism may be a signal configured to reliably transfer the computer program 406. The apparatus may propagate or transmit the computer program 406 as a computer data signal.

In some examples, a computer program 406 when run on a terminal node 110 causes: storing received configuration information defining at least: a handover execution condition 22 for a primary cell; multiple addition conditions 32 for multiple primary secondary cells for dual connectivity with the primary cell, wherein the addition conditions 32 comprise at least: an addition condition 32 for a first one of multiple primary secondary cells for dual connectivity with the primary cell; and an addition condition 32 for a second one of multiple primary secondary cells for dual connectivity with the primary cell; and enabling conditional handover with dual connectivity using the configuration information.

In other examples, a computer program 406 when run by a network node 120 causes: transmitting configuration information, the configuration information defining at least: a handover execution condition 22 for a primary cell; multiple addition conditions 32 for multiple primary secondary cells for dual connectivity with the primary cell, wherein the multiple addition conditions 22 comprise at least: an addition condition 32 for a first one of multiple primary secondary cells for dual connectivity with the primary cell; and an addition condition 32 for a second one of multiple primary secondary cells for dual connectivity with the primary cell; enabling conditional handover with dual connectivity based on the configuration information.

The computer program instructions may be comprised in a computer program, a non- transitory computer readable medium, a computer program product, a machine readable medium. In some but not necessarily all examples, the computer program instructions may be distributed over more than one computer program.

Although the memory 404 is illustrated as a single component/circuitry it may be implemented as one or more separate components/circuitry some or all of which may be integrated/removable and/or may provide permanent/semi-permanent/ dynamic/cached storage.

Although the processor 402 is illustrated as a single component/circuitry it may be implemented as one or more separate components/circuitry some or all of which may be integrated/removable. The processor 402 may be a single core or multi-core processor.

References to ‘computer-readable storage medium’, ‘computer program product’, ‘tangibly embodied computer program’ etc. or a ‘controller’, ‘computer’, ‘processor’ etc. should be understood to encompass not only computers having different architectures such as single /multi- processor architectures and sequential (Von Neumann)/parallel architectures but also specialized circuits such as field-programmable gate arrays (FPGA), application specific circuits (ASIC), signal processing devices and other processing circuitry.

References to computer program, instructions, code etc. should be understood to encompass software for a programmable processor or firmware such as, for example, the programmable content of a hardware device whether instructions for a processor, or configuration settings for a fixed-function device, gate array or programmable logic device etc. As used in this application, the term ‘circuitry’ may refer to one or more or all of the following:

(a) hardware-only circuitry implementations (such as implementations in only analog and/or digital circuitry) and

(b) combinations of hardware circuits and software, such as (as applicable):

(i) a combination of analog and/or digital hardware circuit(s) with software/firmware and

(ii) any portions of hardware processor(s) with software (including digital signal processor(s)), software, and memory(ies) that work together to cause an apparatus, such as a mobile phone or server, to perform various functions and

(c) hardware circuit(s) and or processor(s), such as a microprocessor(s) or a portion of a microprocessor(s), that requires software (e.g. firmware) for operation, but the software may not be present when it is not needed for operation.

This definition of circuitry applies to all uses of this term in this application, including in any claims. As a further example, as used in this application, the term circuitry also covers an implementation of merely a hardware circuit or processor and its (or their) accompanying software and/or firmware. The term circuitry also covers, for example and if applicable to the particular claim element, a baseband integrated circuit for a mobile device or a similar integrated circuit in a server, a cellular network device, or other computing or network device.

The blocks illustrated in the Figs may represent steps in a method and/or sections of code in the computer program 406. The illustration of a particular order to the blocks does not necessarily imply that there is a required or preferred order for the blocks and the order and arrangement of the block may be varied. Furthermore, it may be possible for some blocks to be omitted.

Where a structural feature has been described, it may be replaced by means for performing one or more of the functions of the structural feature whether that function or those functions are explicitly or implicitly described.

The above described examples find application as enabling components of: automotive systems; telecommunication systems; electronic systems including consumer electronic products; distributed computing systems; media systems for generating or rendering media content including audio, visual and audio visual content and mixed, mediated, virtual and/or augmented reality; personal systems including personal health systems or personal fitness systems; navigation systems; user interfaces also known as human machine interfaces; networks including cellular, non-cellular, and optical networks; ad-hoc networks; the internet; the internet of things; virtualized networks; and related software and services.

The term ‘comprise’ is used in this document with an inclusive not an exclusive meaning. That is any reference to X comprising Y indicates that X may comprise only one Y or may comprise more than one Y. If it is intended to use ‘comprise’ with an exclusive meaning then it will be made clear in the context by referring to “comprising only one..” or by using “consisting”.

In this description, reference has been made to various examples. The description of features or functions in relation to an example indicates that those features or functions are present in that example. The use of the term ‘example’ or ‘for example’ or ‘can’ or ‘may’ in the text denotes, whether explicitly stated or not, that such features or functions are present in at least the described example, whether described as an example or not, and that they can be, but are not necessarily, present in some of or all other examples. Thus ‘example’, ‘for example’, ‘can’ or ‘may’ refers to a particular instance in a class of examples. A property of the instance can be a property of only that instance or a property of the class or a property of a sub-class of the class that includes some but not all of the instances in the class. It is therefore implicitly disclosed that a feature described with reference to one example but not with reference to another example, can where possible be used in that other example as part of a working combination but does not necessarily have to be used in that other example.

Although examples have been described in the preceding paragraphs with reference to various examples, it should be appreciated that modifications to the examples given can be made without departing from the scope of the claims.

Features described in the preceding description may be used in combinations other than the combinations explicitly described above.

Although functions have been described with reference to certain features, those functions may be performable by other features whether described or not.

Although features have been described with reference to certain examples, those features may also be present in other examples whether described or not. The term ‘a’ or ‘the’ is used in this document with an inclusive not an exclusive meaning. That is any reference to X comprising a/the Y indicates that X may comprise only one Y or may comprise more than one Y unless the context clearly indicates the contrary. If it is intended to use ‘a’ or ‘the’ with an exclusive meaning then it will be made clear in the context. In some circumstances the use of ‘at least one’ or ‘one or more’ may be used to emphasis an inclusive meaning but the absence of these terms should not be taken to infer any exclusive meaning.

The presence of a feature (or combination of features) in a claim is a reference to that feature or (combination of features) itself and also to features that achieve substantially the same technical effect (equivalent features). The equivalent features include, for example, features that are variants and achieve substantially the same result in substantially the same way. The equivalent features include, for example, features that perform substantially the same function, in substantially the same way to achieve substantially the same result.

In this description, reference has been made to various examples using adjectives or adjectival phrases to describe characteristics of the examples. Such a description of a characteristic in relation to an example indicates that the characteristic is present in some examples exactly as described and is present in other examples substantially as described.

Whilst endeavoring in the foregoing specification to draw attention to those features believed to be of importance it should be understood that the Applicant may seek protection via the claims in respect of any patentable feature or combination of features hereinbefore referred to and/or shown in the drawings whether or not emphasis has been placed thereon. l/we claim:

Claims

33 CLAIMS

1. An apparatus comprising means for: receiving configuration information comprising at least a handover execution condition for a primary cell; multiple addition conditions for multiple primary secondary cells for dual connectivity with the primary cell, wherein the addition conditions comprise at least: an addition condition for a first one of multiple primary secondary cells for dual connectivity with the primary cell; and an addition condition for a second one of multiple primary secondary cells for dual connectivity with the primary cell; and enabling conditional handover with dual connectivity using the configuration information.

2. An apparatus as claimed in claim 1 , comprising means for: performing a measurement for a handover execution condition for a primary cell; and performing separate measurements for the multiple addition conditions for the multiple primary secondary cells for dual connectivity with the primary cell.

3. An apparatus as claimed in claim 2, comprising means for selecting one of the multiple primary secondary cells for conditional handover with dual connectivity, at least partially based on the the handover execution condition; the multiple addition conditions; and the multiple measurements.

4. An apparatus as claimed in claim 3, comprising means for selecting one of the multiple primary secondary cells for conditional handover with dual connectivity, at least partially based on a further condition.

5. An apparatus as claimed in claim 3 or 4, comprising means for informing a network of the selection.

6. An apparatus as claimed in any preceding claim, comprising means for determining if the handover execution condition for the primary cell is met and for determining if the 34 addition condition for only one of multiple primary secondary cells is met, and means for enabling completion of conditional handover with dual connectivity to the primary cell and the one of multiple primary secondary cells if the handover execution condition for the primary cell is met and the addition condition for the only one of multiple primary secondary cells is met.

7. An apparatus as claimed in any preceding claim, comprising means for enabling completion of conditional handover without dual connectivity to the primary cell and enabling initiation, but not completion, of handover with dual connectivity to a selected primary secondary cell.

8. An apparatus as claimed in any preceding claim, wherein the configuration information comprises: configuration information for handover to the primary cell configuration information for dual connectivity to any of the multiple primary secondary cells.

9. A method comprising: receiving configuration information comprising at least: a handover execution condition for a primary cell; multiple addition conditions for multiple primary secondary cells for dual connectivity with the primary cell, wherein the addition conditions comprise at least: an addition condition for a first one of multiple primary secondary cells for dual connectivity with the primary cell; and an addition condition for a second one of multiple primary secondary cells for dual connectivity with the primary cell; and enabling conditional handover with dual connectivity using the configuration information.

10. A computer program that when run a terminal node causes: storing received configuration information defining at least: a handover execution condition for a primary cell; multiple addition conditions for multiple primary secondary cells for dual connectivity with the primary cell, wherein the addition conditions comprise at least: an addition condition for a first one of multiple primary secondary cells for dual connectivity with the primary cell; and an addition condition for a second one of multiple primary secondary cells for dual connectivity with the primary cell; and enabling conditional handover with dual connectivity using the configuration information.

11. An apparatus comprising means for: transmitting configuration information, the configuration information comprising at least: a handover execution condition for a primary cell; multiple addition conditions for multiple primary secondary cells for dual connectivity with the primary cell, wherein the multiple addition conditions comprise at least: an addition condition for a first one of multiple primary secondary cells for dual connectivity with the primary cell; and an addition condition for a second one of multiple primary secondary cells for dual connectivity with the primary cell; enabling conditional handover with dual connectivity using the configuration information.

12. An apparatus as claimed in claim 11 , configured to operate as a serving master node, transmitting configuration information to a user equipment.

13. An apparatus as claimed in claim 11, configured to operate as a candidate serving master node, transmitting configuration information to a serving master node for onward transmission to the user equipment.

14. A method comprising: transmitting configuration information, the configuration information comprising at least: a handover execution condition for a primary cell; multiple addition conditions for multiple primary secondary cells for dual connectivity with the primary cell, wherein the multiple addition conditions comprise at least: an addition condition for a first one of multiple primary secondary cells for dual connectivity with the primary cell; and an addition condition for a second one of multiple primary secondary cells for dual connectivity with the primary cell; enabling conditional handover with dual connectivity using the configuration information.

15. A computer program that when run by a network node causes: transmitting configuration information, the configuration information defining at least: a handover execution condition for a primary cell; multiple addition conditions for multiple primary secondary cells for dual connectivity with the primary cell, wherein the multiple addition conditions comprise at least: an addition condition for a first one of multiple primary secondary cells for dual connectivity with the primary cell; and an addition condition for a second one of multiple primary secondary cells for dual connectivity with the primary cell; enabling conditional handover with dual connectivity based on the configuration information.