Patent Description:
Fifth generation (<NUM>) wireless communications networks are the next generation of mobile communications networks. Standards for <NUM> communications networks are currently being developed by the Third Generation Partnership Project (3GPP). These standards are known as 3GPP New Radio (NR) standards.

Document <CIT> discloses conditional handover based on a target cell for handover being one of multiple candidate cells for handover meeting a predetermined condition relative to other candidate cells.

The present invention provides for a user equipment and a corresponding method as set out in the accompanying claims.

The example embodiments and features, if any, described in this specification that do not fall under the scope of the independent claims are to be interpreted as examples useful for understanding various example embodiments of the invention.

A Conditional Handover (CHO) has two phases. A configured event triggers a user equipment (UE) to send a measurement report. Based on this report, a source cell prepares a target for the handover, which includes a handover request and handover request acknowledgement. The source cell then sends a CHO command to the UE.

In systems, utilizing dual connectivity (DC), a target configuration may include multiple cells.

For a legacy HO, the UE will access the target cell to complete the handover. However, for CHO, the UE will access the target once an additional CHO execution condition is met. The condition is typically configured by the source cell as part of the CHO command.

The inventors have discovered that interference caused by a multiple cell target to target neighbor cells is not considered. For example, when a mobility event such as A3 is evaluated, a cell individual offset (CIO) is considered (3GPP TS <NUM> section <NUM>. <NUM>, Release <NUM>). However, the CIO is evaluated for the imbalance/difference in signal strength between source and target cells, not for cells within a target, nor as an imbalance/difference in signal strengths for cells neighboring the target cell.

Example embodiments will become more fully understood from the detailed description given herein below and the accompanying drawings, wherein like elements are represented by like reference numerals, which are given by way of illustration only and thus are not limiting of this disclosure.

Detailed illustrative embodiments are disclosed herein. However, specific structural and functional details disclosed herein are merely representative for purposes of describing example embodiments. The example embodiments may, however, be embodied in many alternate forms and should not be construed as limited to only the embodiments set forth herein.

It should be understood that there is no intent to limit example embodiments to the particular forms disclosed. On the contrary, example embodiments are to cover all modifications, equivalents, and alternatives falling within the scope of this disclosure. Like numbers refer to like elements throughout the description of the figures.

While one or more examples may be described from the perspective of network nodes (e.g., radio access network (RAN) elements, base stations, eNBs, gNBs, Central Units (CUs), ng-eNBs, WLAN access points or controllers, etc.), user equipment (UE), or the like, it should be understood that one or more examples discussed herein may be performed by the one or more processors (or processing circuitry) at the applicable device. For example, according to one or more examples, at least one memory may include or store computer program code, and the at least one memory and the computer program code may be configured to, with at least one processor, cause a network node to perform the operations discussed herein. As discussed herein, UE and User may be used interchangeably. Moreover, a UE or User may be referred to as being served by the node or cell when the UE or User is within the cell and the node is providing wireless resources for transmission to/from the UE or User. In WLAN networks a UE or User may be a station (STA).

Further, some examples are applicable also to cells which are set up by UEs, such as UEs which have the ability to act as a gNB. Some example embodiments are also applicable to relay nodes, such as Integrated Access Backhaul (IAB) nodes. It may be applicable to New Radio Unlicensed (NR-U) nodes and UEs. Some example embodiments are may be applicable also to device-to-device (D2D) communications. Some example embodiments are be applicable to MulteFire systems. In general, some example embodiments are apply to situations where CHO is used for multi-cell targets.

It will be appreciated that a number of examples may be used in combination.

Throughout the description, a cell of a particular network node (e.g., base station, eNB, gNB, ng-eNB) is described as a "serving cell" or "source cell" for a particular UE. The transmissions to and from the UE are served through the network node, and the coverage area of the network node can be termed as the "serving cell" or "source cell" of the UE. We may use the term 'cell' to refer to either the coverage area of transmission of a particular network node, or the network node itself, depending on the context. Typically, the area within which the transmissions of the neighbor network nodes can be received will have some overlap with the area within which the transmissions of a serving network node can be received. A UE may be able to also receive transmissions from one or more network nodes in a neighbor set. Conversely, it may be possible to receive the signal of a given UE's uplink transmissions at not only its serving cell but also at one or more neighbor cells.

<FIG> illustrates an example of a conditional handover.

At S150, a source cell sends a measurement control to a UE. The measurement control configures the measurement procedures for the UE. At S155, the UE responds to the measurement control by generating and sending a measurement report to the source cell. At S157, the source cell decides whether to use a CHO to hand off the UE. In some example embodiments, the source cell decides whether to use the CHO based on the measurement report received at S155 and radio resource management (RRM) information. In addition to or as an alternative, the source cell may decide whether to use the CHO based on whether the UE is connected to the source cell. If the source cell decides to use a CHO to hand off the UE, at S160, the source cell generates and sends a CHO request to one or more target cells based on the measurement report which the CHO target cell(s) belong to. Upon receiving the CHO request, the target cell(s) perform admission control.

At S170, the target cell acknowledges the handover request and is prepared to receive communications from the UE. Upon receiving the handover request acknowledgement from the target cell, the source cell sends a CHO command to the UE at S180. The CHO command serves the purpose to allow a UE to react more quickly to changing conditions and select a new source cell. However, the UE evaluates conditions for selecting a new source cell which in a normal HO would have been carried out by the existing source cell.

In the CHO command, a RRCReconfiguration, as set forth in 3GPP TS <NUM> Release <NUM>, is prepared by the source cell and provided to the UE. The RRCreconfiguration may contain the configuration for multiple cells, for carrier aggregation (CA) or for dual connectivity (DC). The configuration for multiple cells is included in the RRCReconfiguration for instance as a set of parameters in the information element (IE) CellGroupConfiguration. In CA, the HO happens first to a target primary cell (PCell), and secondary cells (SCells) are de-activated after HO. The target PCell activates the SCells.

In DC, the CHO happens to the target PCell, in the sense that a radio resource control (RRC) connection is established between the PCell and the UE. The PCell then performs a PSCell addition procedure which initiates the establishment of a connection between the PSCell and the UE. The PSCell and the UE will also have an RRC connection. The RRC connection between the PSCell and UE may be routed via the PCell, or directly via a signaling radio bearer (SRB) between the UE and the PSCell.

In some examples, a DC HO command received by the UE may cause the UE to establish connection to PCell and PSCell in parallel, e.g. by performing random access procedures to both in parallel. Thus, multi-cell target configurations can be provided in a CHO command, because the source cell has evaluated the suitability of the target cells based on the UE's measurements and other information available to the source cell. In some example embodiments, the source cell has evaluated the suitability of the target cell prior to issuing the CHO command to the UE.

At S185, the UE maintains connection with the source cell after receiving the CHO command and starts to evaluate the CHO target cell(s). More specifically, the UE monitors communications for the condition to be satisfied. Once the UE determines the condition is satisfied by a CHO target cell, the UE initiates the handover to the target cell by performing a random access procedure with the target cell at S190. When the handover is complete, the UE acknowledges the handover by generating and sending a handover complete acknowledgement to the target cell at S195 (e.g., a RRCConnectionReconfigurationComplete message as set forth in 3GPP TS <NUM>, Release <NUM>).

<FIG> illustrates a simplified diagram of a portion of a Third Generation Partnership Project (3GPP) New Radio (NR) access deployment.

Referring to <FIG>, the 3GPP NR radio access deployment includes a gNB (or node) <NUM> having transmission and reception points (TRPs) 102A and 102B and a gNB (or node) <NUM> having TRPs 202A and 202B. Each TRP 102A, 102B, 202A, 202B may be, for example, a remote radio head (RRH) or remote radio unit (RRU) including at least, for example, a radio frequency (RF) antenna (or antennas) or antenna panels, and a radio transceiver, for transmitting and receiving data within a geographical area. In this regard, the TRPs 102A, 102B, 202A, 202B provide cellular resources for user equipment (UEs) within a geographical coverage area referred to as a cell. In the example shown in <FIG>, the TRPs 102A, 102B, 202A, 202B are configured to communicate with one or more UEs (e.g., UE or User <NUM>) via one or more transmit (TX)/receive (RX) beam pairs. The gNBs <NUM> and <NUM> communicate with the core network, which may be referred to as the Next Generation Core (NGC) in 3GPP NR.

The TRPs 102A, 102B, 202A, 202B may have independent schedulers, or the gNBs <NUM> and <NUM> may perform joint scheduling among their respective TRPs.

Although only a single UE <NUM> is shown in <FIG>, the gNBs <NUM> and <NUM> and their respective TRPs 102A, 102B, 202A, 202B may provide communication services to a relatively large number of UEs within a cell.

<FIG> illustrate systems having dual connectivity.

<FIG> illustrates an Evolved-Universal Terrestrial Radio Access-New Radio dual connectivity (EN-DC) system. As shown in <FIG>, a UE <NUM> may communicate with an evolved NodeB (eNB) <NUM> and a next generation NodeB (gNB) <NUM>. In the EN-DC system of <FIG>, the eNB <NUM> functions as a primary node and the gNB <NUM> functions as a secondary node. Thus, communications with the UE <NUM> and the eNB <NUM> occur across a user plane <NUM> and a control plane <NUM> via a Uu interface <NUM>. Communications between the UE <NUM> and the gNB <NUM> occur across a user plane <NUM> via a Uu interface <NUM>. Communication between the UE <NUM> and the gNB <NUM> (e.g., a PSCell) may happen also via an SRB (SRB3), providing a control plane connection <NUM> via the Uu interface <NUM>. The eNB <NUM> and the gNB <NUM> communicate over an X2 control (X2-C) interface <NUM> and an X2 user (X2-U) interface <NUM>. Both the eNB <NUM> and the gNB <NUM> communicate with an evolved packet core (EPC) <NUM>. The eNB <NUM> communicates with the EPC <NUM> over an S1 control (S1-C) interface <NUM> and an S2 user (S1-U) interface <NUM>. The gNB <NUM> communicates with the EPC <NUM> over an S1-U <NUM>.

<FIG> illustrates a New Radio dual connectivity (NR DC) system. As shown in <FIG>, the UE <NUM> may communicate with a gNB <NUM> and a gNB <NUM>. In the NR DC system of <FIG>, the gNB <NUM> functions as a primary node and the gNB <NUM> functions as a secondary node. The gNB <NUM> provides a primary cell (PCell) and the gnB <NUM> provides a primary secondary cell (PSCell). Thus, communications with the UE <NUM> and the gNB <NUM> occur across a user plane <NUM> and a control plane <NUM> via a Uu interface <NUM>. Communications between the UE <NUM> and the gNB <NUM> occur across a user plane <NUM> via a Uu interface <NUM>. Communication between the UE and the PSCell may happen also via an SRB (SRB3), providing a control plane connection <NUM> via the Uu interface <NUM>. The gNB <NUM> and the gNB <NUM> communicate over an Xn control (Xn-C) interface <NUM> and an Xn user (Xn-U) interface <NUM>. Both the gNB <NUM> and the gNB <NUM> communicate with a next generation core (NGC) <NUM>. The gNB <NUM> communicates with the NGC <NUM> over a next generation control (NG-C) interface <NUM> and a next generation user (NG-U) interface <NUM>. The gNB <NUM> communicates with the NGC <NUM> over an NG-U <NUM>. The gNB <NUM> may also be an eNB with the ability to have an Xn and NG interface.

In CA, a single gNB (e.g., the gNB <NUM>) has a NG connection to the NGC and the Uu interface to the UE <NUM>. The single gNB establishes multiple cells on different frequencies. One of established cells is the Master cell which carries the RRC connection. The cells may be overlapping in coverage, or may be separated by remote radio heads.

<FIG> illustrates an NR or LTE DC system having multiple DC configurations.

The CHO command will contain the configuration for a possible HO target. The target is thus a cell or a group of cells in a CA or DC configuration. In a CHO it is possible that not only a single but multiple targets are provided to the UE in the CHO command or separate CHO commands. Thus, the UE is enabled to evaluate a HO condition to different targets coming into view based on its trajectory.

A gNB or eNB may be aware of its neighbors as it is, e.g., providing measurement configurations referring to neighbors to the UE, and also issuing HO commands for neighbors to the UE, and communicating with its neighbors via the Xn or X2 interface. A gNB may also have neighbors but not an Xn interface with those neighbors. A gNB or eNB may also be aware of its neighbors' neighbors. This is possible by corresponding signaling on the Xn interface, where the neighbors may exchange a list of records, each record of a neighbor providing information including a physical cell identifier (PCI), cell global identity (CGI), tracking area code (TAC), and more.

The neighbor information can be exchanged as information elements. In some example embodiments, the neighbor information may be exchanged as part of the XnSetup procedure in the NeighbourInformation IE which is in the ServedCells IE, as set forth in 3GPP TS <NUM>, Release <NUM>. The corresponding information element can be enhanced to carry additional information regarding tolerable imbalance parameters mentioned in some example embodiments. In some example embodiments, the information element could be exchanged using new procedures not only relying on the XnSetup.

As shown in <FIG>, a dual connectivity group <NUM> and dual connectivity group <NUM> communicate with each other through an Xn interface <NUM>. The Xn interface <NUM> may include user plane and control plane communications. The dual connectivity group <NUM> includes a gNB <NUM> providing a PCell and a gNB <NUM> providing a PSCell. The gNB <NUM> and the gNB <NUM> communicate with each other and the NGC <NUM> in a similar manner as described in <FIG>. The dual connectivity group <NUM> includes a gNB <NUM> providing a PCell and a gNB <NUM> providing a PSCell. The gNB <NUM> and the gNB <NUM> communicate with each other and the NGC <NUM> in a similar manner as described in <FIG>.

More specific details of examples will be described herein with regard to the 3GPP NR access deployment shown in <FIG>. Although various access deployments have been shown in <FIG> and <FIG>, the following discussion may refer to eNBs and gNBs more generically as cells or network nodes. Moreover, it should be understood that examples should not be limited to the example access deployments illustrated in <FIG> and <FIG>.

<FIG> illustrates a system having two potential targets for a handover. As shown in <FIG>, a UE <NUM> communicates with a source cell <NUM>. Based on the location of the UE <NUM>, the UE <NUM> has a first target configuration <NUM> for handover and a second target configuration <NUM> for handover.

In the example shown in <FIG>, the first target configuration <NUM> includes a cell <NUM> and a cell <NUM> that are configured to provide dual connectivity. The cell <NUM> can operate as a PCell and can provide a primary cell of coverage <NUM>. The cell <NUM> can operate as a PSCell and can provide a primary secondary cell of coverage <NUM>. While the secondary cell of coverage <NUM> is illustrated as being completely within the primary cell of coverage <NUM>, examples are not limited therein.

An RRC Reconfiguration contains a secondaryCellGroup IE and a masterCellGroup IE, each containing a SpCell IE which configures a primary cell (PCell or PSCell). Thus, a UE can be provided with information about a potential PCell and PScell.

It should be understood that a primary cell of coverage and a secondary cell of coverage may partially overlap or not overlap.

The second target configuration <NUM> includes a cell <NUM> and a cell <NUM> that are configured to provide dual connectivity. The cell <NUM> can operate as a PCell and provides a primary cell of coverage <NUM>. The cell <NUM> can operate as a PSCell and provides a primary secondary cell over coverage <NUM>.

When handing over to a target configuration having a multi-cell configuration, a cell within the target configuration may exhibit a weaker strength compared to other neighboring cells using the same frequency. This may lead to a higher interference coming from the intra-frequency neighboring cells.

For example, if a handover occurs from the source cell <NUM> to the first target configuration <NUM> comprising cell <NUM> because the first target configuration <NUM> has a higher guaranteed bitrate (GBR) than the second target configuration <NUM>, uplink (UL) interference will occur if the UE <NUM> is closer to the target cell <NUM> than the target cell <NUM> and the target cell <NUM> and the target cell <NUM> use the frequency/carrier/subband. Moreover, communications from the target cell <NUM> will create downlink (DL) interference for communications transmitted by the target cell <NUM> and received by the UE <NUM>.

When mobility event such as A3 is evaluated, a cell individual offset (CIO) is also considered, such as described in 3GPP TS <NUM> section <NUM>. <NUM>, Release <NUM>. However, the CIO is evaluated for the imbalance/difference in signal strength between source and target cells, not for cells within the target configuration, nor as an imbalance/difference in signal strengths for cells neighboring the target.

Thus, at least some examples use an interference related margin with respect to neighboring cells on a frequency/carrier/subband during a CHO. The margin may be specific to a neighbor of a cell in the target using a same frequency. Moreover, the margin may be set by a target cell of the handover based on tolerable interference.

Currently, events apply to cells belonging to a single target cell of handover, not an aggregate quality, nor neighboring cells of a target cell.

A CHO condition may be based on evaluating the received signal strength of several possible target cells provided in the measurement configuration against a received signal strength of the source cell. With existing mechanisms, a strongest cell on a given frequency can be selected by basing a HO decision on a measurement of a single cell such as reference signal received power (RSRP) or reference signal received quality (RSRQ). This avoids creating undue interference to other cells.

With the introduction of multi-cell targets, there may be some cells among the cells of the ultimately chosen target which are weaker than cells neighboring targets. For example, if a DC target is selected based only on a RSRP of a PCell in the selected target, a large imbalance in strength of the PSCell (being on a different frequency) of the selected target to an intra-frequency neighbor of the PSCell cell may exist.

Furthermore, in CHO, measurements taken earlier and reported to the gNB by the UE may be out-of-date at the time the condition is met.

In some examples, a condition to carry out a CHO to a HO target including multiple cells includes an interference related margin to other neighboring cells on a specific frequency/carrier/subband. The margin may be specific to a neighbor of a cell in the target configuration using the same frequency. The margin is communicated to the UE as part of the CHO command. In some examples, the margin can be set by the target cell's neighbor. In other examples, the margin can be set by the target cell when the target cell knows about its neighbor's allowed interference related margin. The margin can be set to a default value by the source cell.

The first target configuration <NUM> includes a cell <NUM> and a cell <NUM> that are configured to provide dual connectivity. The cell <NUM> can operate as a PCell and provides a primary cell of coverage <NUM>. The cell <NUM> can operate as a PSCell and provides a primary secondary cell of coverage <NUM>.

The second target configuration <NUM> includes a cell <NUM>. The cell <NUM> provides a cell of coverage <NUM>. The cell <NUM> provides a cell neighboring the target configuration <NUM>. While the second target configuration <NUM> does not illustrate multiple cells, examples are not limited thereto. Moreover, while the first target configuration <NUM> is illustrated as a DC configuration, it should be understood that examples are not limited thereto and may be implemented in targets having a CA configuration or cells being on different frequencies.

In the system of <FIG>, both the cell <NUM> and the cell <NUM> use a same frequency f1 (e.g., operating on a same carrier as a download frequency, an upload frequency or both). The cell <NUM> uses a frequency f2.

In the system, a CHO may be performed by the source cell <NUM>, the UE <NUM> and any one of the cells <NUM>, <NUM> and <NUM> using an interference related margin as shown in <FIG>.

<FIG> is a flow chart illustrating a method.

At S450, the source cell <NUM> generates a CHO request and transmits the CHO request to the cell <NUM>. The source cell <NUM> generates the CHO request based on the connection between the UE and the source cell. The source cell <NUM> may send CHO requests to all of its neighbors, i.e., also cell <NUM>. In some examples, if the source cell <NUM> has earlier received measurement reports from the UE <NUM> (not shown in the <FIG>), the source cell <NUM> may choose to send a CHO request only to targets whose strength reported by the UE <NUM> is above a threshold. The target cell <NUM>, based on the CHO request sent at S450, performs admission control, reserves resources and takes other steps used in a HO for the UE <NUM>. In at least one example, the target cell <NUM> further prepares the cell <NUM> for the CHO of the UE <NUM> based on the CHO request sent at S450 (not shown in <FIG>). In another example, the source cell <NUM> sends a separate CHO request to cell <NUM> (not shown in <FIG>).

At S455, the cell <NUM> responds to the request by generating and transmitting a CHO acknowledgement to the source cell <NUM>. In the CHO acknowledgement, the cell <NUM> includes a permitted performance margin. If the cell <NUM> is aware of the cell <NUM>, the cell <NUM> may include a permitted performance margin for the cell <NUM> in the CHO acknowledgement. Moreover, the cell <NUM> may include information regarding permitted performance margins of cells in the same target. For example, the cell <NUM> may include information regarding a permitted performance margin of the cell <NUM>. In another example, if the source cell <NUM> has sent separate CHO requests to target cells <NUM> and <NUM>, and the cell <NUM> is aware of the performance margin of its neighbor cell <NUM>, the cell <NUM> can include the permitted performance margin associated with the cell <NUM> in the CHO acknowledgment.

The permitted performance margin may be a threshold interference level or a maximum UL transmit power associated with the neighbor cell, but is not limited thereto. The threshold interference level and maximum UL transmit power are values determined by the neighbor cell and are values the neighbor cell can tolerate from a UE that is served by a particular cell other than the neighbor cell.

In some examples, the permitted performance margin is for a particular frequency and may be a UE measured strength (e.g., RSRP) of a target cell (e.g., cell <NUM>) relative to a neighboring cell strength (e.g., RSRP) in a neighboring target on the same frequency (e.g., cell <NUM>). In such examples, the permitted performance margin is a signal offset expressed in dB.

As an alternative to providing the permitted performance margin in the CHO acknowledgement at S455, the source cell <NUM> may generate a query separate from the CHO request for the permitted performance margin and send the query to the cell <NUM>. The cell <NUM> may respond to the query by sending the permitted performance margin of the cell <NUM> to the source cell <NUM>. In some examples, the signaling of the query and permitted performance is relayed via the Xn interface using, for example, the Xn Application Protocol (XnAP) protocol. The source cell <NUM> may also query the cell <NUM> in a similar fashion. The queried cell may respond the query if it has obtained a NeighbourInformation IE comprising the permitted performance margin of its neighbor cell <NUM>.

Each cell may determine a permitted performance margin based on based on adaptive and learning algorithms, which consider the interference in the cell, the load in the cell, and the UE or system performance. For example, a cell may alter its associated permitted performance margin based on a number of UEs the cell is serving. The cell may indicate a relatively larger permitted performance margin when serving a relatively smaller number of UEs (and/or with relatively smaller load) compared to indicating a relatively lower permitted performance margin when serving a relatively larger number of UEs (and/or with relatively larger load). The load of a cell may be the percentage of used resource blocks or an average SINR of communications between the cell and the UEs being served by the cell. In a case of unlicensed spectrum, the load it may be a channel occupancy as seen by network node or seen by UEs connected to the network node.

The CHO acknowledgment may contain the HO command for the UE. Thus, the CHO acknowledgement may contain the multi-cell target configuration.

The target cell <NUM> can be aware of its neighbors, the possibility to establish DC connections, and neighbors of DC connections based on network higher layer configuration, such as operations, administration and management (OAM). Moreover, the target cell <NUM> can be aware of neighbors' neighbors using Xn signaling without OAM, as described above.

In other examples, the cell may use a default permitted performance margin. The default margin may be that used also for the HO to a target cell, that is the offset that is applied to the difference between serving and target cell when evaluating which cell is stronger. In some examples, the default permitted performance margin may be <NUM> dB.

If the source cell <NUM> does not receive a permitted performance margin for a target's neighboring cells, the cell <NUM> sends queries to neighboring cells of the target for which a permitted performance margin has not been received. For example, if the source cell <NUM> does not receive a permitted performance margin for the cell <NUM> at S455, the cell <NUM> will query the cell <NUM> for the permitted performance margin of the cell <NUM> at S460.

At S465, the cell <NUM> responds to the query by transmitted a permitted performance margin to the source cell <NUM>. The signaling of the query and the permitted performance margin may be carried out by the source cell <NUM> and the cell <NUM> using the XnAP.

At S470, the source cell <NUM> sends a CHO command to the UE <NUM>. The command indicates the configuration of the first target configuration <NUM> and contains the permitted performance margin for the cell <NUM> on the frequency f1.

At S475, the UE <NUM> evaluates the CHO condition for the first target configuration <NUM>.

<FIG> is a flow chart illustrating a method of evaluating a CHO condition.

At S505, the UE <NUM> obtains at least one CHO condition from the source cell <NUM>. The at least one CHO condition includes the performance margin associated with the cells (e.g., the cell <NUM>) neighboring the target cell.

At S510, the UE <NUM> performs measurements regarding the cells indicated in the CHO command. More specifically, the UE <NUM> may perform RSRP and RSRQ measurements for each of the cells indicated in the CHO command. In some example embodiments, the CHO command identifies target cells, and conditions to be fulfilled. The conditions refer to one or more of the target cells. The UE performs evaluation of the conditions in the CHO command. In the example of <FIG>, the UE <NUM> measures the RSRP and/or RSRQ for the cell <NUM>, the cell <NUM> and the cell <NUM>.

At S515, the UE <NUM> tentatively selects a target configuration for HO based on a condition being satisfied. For example, assuming part of the conditions is an A3 event for the serving and one of the target configuration cells, the UE <NUM> tentatively selects the first target configuration <NUM> when an A3 event occurs for the cell <NUM>.

The UE <NUM> determines whether DL transmissions from the cells in the targets neighboring the selected target are within the permitted performance margin of the UE <NUM> at S525.

The UE <NUM> measures a RSRP from the target cell <NUM> and a RSRP from the cell <NUM>. The UE <NUM> determines a difference between the RSRP from the target cell <NUM> and the RSRP from the cell <NUM>. The UE <NUM> then compares the difference to the permitted performance margin associated with the target cell <NUM> and the cell <NUM>. If the difference is less than the permitted performance margin, the DL transmissions from the cell <NUM> are within the permitted performance margin.

If the UE <NUM> determines the DL transmissions from any one of the cells in the targets neighboring the selected target are not within the permitted performance margin, the method proceeds back to S510 where the UE <NUM> performs measurements again.

Pseudo code for S525 may be:
for all freq f_i that are contained in the selected target configuration create list L(f_i) of cells neighboring to target cell c_target(f_i) on freq f_i for all cells c_neighbor(f_i)in L(f_i) evaluate c_neighbor(f_i) permissible performance margin to c_target(f_i).

If the UE <NUM> determines the DL transmissions from the cells in the targets neighboring the selected target are within the permitted performance margin, the UE <NUM> performs the HO with the selected target (i.e., target configuration <NUM>) at S530.

In the above example of <FIG>, the cell <NUM> had one neighbor, the cell <NUM>, using the same frequency and the cell <NUM> has no neighbor using the same frequency. However, it should be understood all cells may have neighbors on their frequencies. In small cell deployments on a given frequency, some cells may have neighbors and some may not have.

The CIO is a cell-specific offset that is added to the imbalance evaluation of a target cell. Taking HO event A3 as an example: In 3GPP TS <NUM> section <NUM>. <NUM> "event A3: neighbor becomes offset better than SpCell", where a leaving condition occurs when <MAT> where Mn is a measurement result of the neighboring cell, not taking into account any offsets, Ofn is a measurement object specific offset of the reference signal of the neighbor cell (i.e. offsetMO as defined within measObjectNR corresponding to the neighbor cell), Ocn is a cell specific offset of the neighbor cell (i.e. cellIndividualOffset as defined within measObjectNR corresponding to the frequency of the neighbor cell), and set to zero if not configured for the neighbor cell, Mp is a measurement result of the SpCell, not taking into account any offsets, Ofp is a measurement object specific offset of the SpCell (i.e. offsetMO as defined within measObjectNR corresponding to the SpCell), Ocp is a cell specific offset of the SpCell (i.e. cellIndividualOffset as defined within measObjectNR corresponding to the SpCell), and is set to zero if not configured for the SpCell, Hys is the hysteresis parameter for the event (i.e. hysteresis as defined within reportConfigNR for the event), Off is an offset parameter for the event (i.e. a3-Offset as defined within reportConfigNR for the event), Mn, Mp are expressed in dBm in case of RSRP, or in dB in case of RSRQ and RS-SINR, and Ofn, Ocn, Ofp, Ocp, Hys, Off are expressed in dB.

Examples differ from CIO Ocn and Ocp in that the performance margin is not evaluated between the source cell and the target cell of handover but rather between a cell in a target HO configuration and any other neighbor cell using same frequency.

In networks with small cells, multi-connectivity may be a default way of operating or configuring a UE. Thus, choosing one target Primary Cell (PCell) for handover out of several ones based on its cell quality and its corresponding potential Secondary Cell, i.e., that can be configured for Dual Connectivity or Carrier Aggregation (CA) operation, i.e. PSCell or Scell, respectively, improves the network. Considering the signal strength/quality of potential PSCells or SCells in the handover could be beneficial for DC or CA operation where the aggregate performance of the radio links could be more relevant than the signal strength/quality of the individual links.

According to at least some example embodiments, systems use an aggregate measurement of cells which belong to a target configuration as a condition to carry out a CHO. A condition that takes into account a parameter (e.g., RSRP) from at least two cells in a same target configuration including multiple cells (e.g., DC and/or CA) may be referred to as an aggregate condition.

The aggregate measurement will be computed by the UE using measurements of the identified target cells. The way the aggregate measurement is formed and is applied as the aggregate condition may be signaled.

<FIG> illustrates a system having at least one target for a handover.

As shown in <FIG>, a UE <NUM> communicates with a source cell <NUM>. Based on the location of the UE <NUM>, the UE <NUM> has a first target configuration <NUM> for handover.

<FIG> is a flow chart illustrating a handover method using an aggregate measure according to example embodiments.

In some example embodiments, a condition to carry out a CHO comprises an aggregate measurement of several cells which belong to a target configuration. This allows selecting a target configuration which will have overall better performance.

At S705, the source cell <NUM> prepares the cell <NUM> for a CHO by generating and sending a CHO request to the cell <NUM>. The CHO request includes a particular configuration (e.g., DC configuration) determined by the source cell <NUM> and an aggregate condition. The source cell <NUM> may determine the configuration based on measurement reports from the UE <NUM>. The aggregate condition may comprise at least one parameter that is to be used by the when UE determining whether a CHO is to be carried out, such as a threshold. The aggregate condition may include a selection of an algorithm by a network node that determines how the UE evaluates the multiple cells of the target. The set of possible algorithms may be made known to the UE by way of standardization. The condition - selection of algorithm and at least one parameter - is determined by OAM or by the source gNB based on UE capabilities, Quality of Service (QoS) requirements, cell maximal capacities, system load, a subcombination thereof or a combination thereof, for example. The signaling may include parameters to be used by the algorithm, such as which cells are to be summed, and what margins are to be applied. The parameters may include RSRP, RSRQ, SINR, a subcombination thereof or a combination thereof as measurements from target cells for a CHO. In addition to or alternatively, the parameters may include a listen-before-talk (LBT) failure rate, a received signal strength indicator (RSSI), a channel occupancy (CO), a subcombination thereof or a combination thereof.

Example embodiments of algorithms and parameters for the aggregate condition are described in more detail with reference to <FIG>.

In other example embodiments, the aggregate condition may be set to a default value by the source cell <NUM>.

More detailed examples are described below.

At S710, the cell <NUM> transmits a request to the cell <NUM> to add the cell as a PSCell for the CHO. At S715, the cell <NUM> acknowledges that it will be part of the multiple cell target configuration for a CHO.

At S720, the cell <NUM> sends a CHO acknowledgement to the source cell <NUM>. The CHO acknowledgement indicates a DC configuration of the first target configuration <NUM> identifying the PCell and PSCell.

At S725, the source cell <NUM> sends a CHO command to the UE <NUM> indicating the DC configuration of the target configuration (i.e., configuration of the first target configuration <NUM>).

At S730, the UE <NUM> obtains measurements from the cell <NUM> and the cell <NUM> to determine whether the aggregate condition is satisfied and determines to perform a HO to the first target configuration <NUM> when the aggregate condition is satisfied. Example embodiments of measuring an aggregate condition are described in more detail below with reference to <FIG>.

When the UE <NUM> determines that the aggregate condition is satisfied, the UE <NUM> performs access to the cell <NUM> by, for example, using a random access procedure (RACH) or performs a RACH-less access. The performing access is sometimes described as a synchronization with the target.

<FIG> is a flow chart illustrating a method according to example embodiments. More specifically, <FIG> illustrates a method of selecting a target by a UE based on the aggregate condition and aggregate measurements.

At S805, the UE obtains measurements from cells of targets for the parameters of the aggregate condition. For example, the UE obtains an RSRP from cells of targets. The UE may determine an RSRQ, a signal to interference and noise ratio (SINR) or both the RSRQ and then SINR. In some example embodiments, the UE may measure the RSRP, the RSRQ, the SINR, a subcombination thereof or a combination thereof as measurements from target cells in accordance with the aggregate condition of the CHO. In addition to or alternatively, the UE determine an LBT failure rate, a RSSI, a CO, a subcombination thereof or a combination thereof as measurements of target cells in accordance with the aggregate condition of the CHO.

At S810, the UE aggregates the measurements on a per target basis. More specifically, the UE combines the measurements for all cells in a same target configuration. For example, the UE combines (i.e., sums) the RSRP from each cell in a single DC target configuration.

In at least one other example embodiment, the source cell instructs the UE to consider only up to n strongest cells in the target cell (i.e., as part of the aggregate condition) and the UE determines the aggregate measurement as summing only up to the n strongest cells in the target, n<amount of cells in target. If n is one, the aggregate measurement amounts to selecting the strength of the strongest cell. In other example embodiments, the source cell instructs the UE to sum RSRPs from each cell or n strongest RSRPs (i.e., as part of the aggregate condition) and the UE determines the measurement by combining the RSRP from each cell in a first target or combining the n strongest RSRP from each cell in the first target and comparing it to a sum of RSRPs of a second target (of each cell in the second target or n strongest in the second target based on the aggregate condition), or comparing it to the sum of a configuration including the source cell (of each cell in the configuration including the source cell or n strongest in the configuration including the source cell). For example, if the aggregate condition is to sum the n strongest RSRPs of the first target configuration and compare the sum to the n strongest RSRPs of the second target configuration and HO based on which combination is greatest and above a threshold, the UE sums the n strongest RSRPs of the first target configuration and compares the sum to a sum of the n strongest RSRPs in the second target configuration. The UE then compares the larger sum to a threshold and if the larger sum is greater than a threshold (e.g., RSRP of the source cell plus an offset value), the UE performs the HO with a target cell in the target configuration associated with the larger sum.

At S815, the UE selects a target configuration based on the aggregate HO condition and the aggregated measurements for each target configuration.

<FIG> is used to illustrate example embodiments of aggregating measurements on a per target basis. <FIG> illustrates a system having two target configurations for a handover.

As shown in <FIG>, a UE <NUM> communicates with a source cell <NUM>. Based on the location of the UE <NUM>, the UE <NUM> has a first target configuration <NUM> for handover and a second target configuration <NUM> for handover.

The first target configuration <NUM> includes a cell <NUM> and a cell <NUM> that are configured to provide dual connectivity. The cell <NUM> can operate as a primary node and provides a primary cell of coverage <NUM>. The cell <NUM> can operate as a secondary node and provides a primary secondary coverage area <NUM>. While the secondary cell of coverage <NUM> is illustrated as being completely within the primary coverage area <NUM>, example embodiments are not limited therein.

The second target configuration <NUM> includes a cell <NUM> and a cell <NUM> that are configured to provide dual connectivity. The cell <NUM> can operate as a primary node and provides a primary coverage area <NUM>. The cell <NUM> can operate as a secondary node and provides a primary secondary coverage area <NUM>.

The first target configuration <NUM> and the second target configuration <NUM> are configured to provide dual connectivity to a UE.

In some example embodiments, the source cell <NUM> defines the HO condition as an event A3. Assuming the first target configuration <NUM> is in a single target HO scenario, the HO trigger condition is reached if <MAT> where O is an offset. For a multi-cell target, the aggregate measurement may be introduced by scaling the offset such that not a single target cell is considered, but the sum of all target cells. Thus, in the above equation of a traditional A3 event the offset O is replaced by a scaled offset: <MAT>.

This type of scaled offset yields an aggregate condition using an aggregate measurement of the multiple cells of the target: <MAT> which equates to <MAT>.

In the above aggregate condition, the sum is computed by the UE over all cells of the first target configuration <NUM>.

In other example embodiments, the cells in a target configuration can be sorted by the UE according to strength, and the UE may sum the n highest strengths where n is less than the number of cells in the target configuration. If n is one, the UE selects the cell having the highest strength.

The strength of a cell can be the RSRP, RSRQ, SINR, the LBT failure rate, CO, RSSI, a subcombination thereof or a combination thereof, but is not limited thereto.

Example embodiments also provide the use of aggregate measurements with more than one target configuration for a CHO. In the description below: <MAT>.

Using <FIG> as an example embodiment, the UE <NUM> obtains measurements from the first target configuration <NUM> and the second target configuration <NUM> as follows:.

Assuming the strength of the source cell <NUM> is -<NUM> dBm, and the offset O is <NUM> dB. The aggregate condition with aggregate measurements is triggered if <MAT>.

For the first target configuration <NUM> the aggregate condition evaluates as: <MAT>.

For the second target configuration <NUM> the aggregate condition evaluates as: <MAT>.

Hence, in the above example embodiment, the aggregate condition would be fulfilled for the first target configuration <NUM>, but not for the second target configuration <NUM>. By contrast, in a legacy scenario the UE would have selected the cell <NUM> of the second target configuration <NUM> (first target configuration <NUM>: -<NUM> > -<NUM> -<NUM>; target configuration <NUM>: -<NUM> < -<NUM> -<NUM>).

<FIG> is used to illustrate other example embodiments of aggregating measurements on a per target basis. <FIG> illustrates a system having two target configurations for a handover.

The first target configuration <NUM> and the second target configuration <NUM> are not configured to provide dual connectivity to a UE. However, both the cell <NUM> and the cell <NUM> use the same frequency f1 and the cell <NUM> and the cell <NUM> use the same frequency f2.

The UE <NUM> evaluates the handover condition between the source cell <NUM> and the target cells of handover <NUM> and <NUM>. In example embodiments, the UE scales the handover offset for the target cells of handover <NUM> and <NUM> based on the aggregate cell measurements. The following terminology is used:.

The UE <NUM> is configured to determine the A3 event using aggregate cell measurement as follows: <MAT> <MAT> where Oscaled1 is a scaled offset of the offset O for the target cell <NUM> and Oscaled2 is a scaled offset of the offset O for the target cell <NUM>.

The UE <NUM> determines the scaled offset Oscaled1 and the scaled offset Oscaled2 as follows using the abbreviation of Σstrength(cells of target configuration) = Σcells of target: <MAT> <MAT>.

The following provides an example embodiment of the determinations performed by the UE <NUM> to select a target cell for handover using an offset O of 3dB.

If Σcells target <NUM> = sum(cell <NUM>,cell <NUM>) = Σcells target <NUM> = sum(cell <NUM>,cell <NUM>)
then <MAT>.

Consequently no scaling with aggregate cell strength takes place in Example <NUM>.

As a result, the UE <NUM> determines the handover to the cell <NUM> is harder than the handover to the cell <NUM> in Example <NUM>.

In some example embodiments, the UE <NUM> limits the scaling of the offset O as follows: <MAT> where maxScaling is a maximum scaled offset and minScaling is a minimum scaled offset.

The minScaling and maxScaling may be set by OAM and adjusted to avoid a too large imbalance in receive strength between neighbor cells above a threshold level when selecting a cell based on the aggregate measure.

In some example embodiments, the maximum scaled offset maxScaling is <NUM> dB and the minimum scaled offset minScaling is -<NUM> dB. Using <NUM> dB and -<NUM> dB as the maximum and minimum scaled offsets, respectively, and the values from Example <NUM>, the UE <NUM> determines the scaled offset Oscaled1 as: <MAT>.

The following provides an example where the UE <NUM> uses the_maximum and minimum scaled offsets as the max() value. <MAT> then <MAT> and <MAT>.

In some example embodiments, a source cell may instruct a UE to combine multiple Ai events and used the combined Ai events as the CHO condition. An Ai event includes any of the A1-A6 events described in 3GPP <NUM>, Release <NUM>.

In some example embodiments, the source cell may instruct the UE in the CHO command to select a target configuration if a trigger condition A4 of a PCell of the target configuration and trigger condition A4 of a PSCell of the target configuration are both met.

In other example embodiments, the source cell may instruct the UE in the CHO command to compare a same type of event from multiple target configurations. The source cell may instruct the UE to monitor an A3 event from a PCell of a first target configuration and monitor an A3 even from a PCell of a second target configuration. If A3 events occur for both the first target configuration and the second target configuration, the UE selects the first target configuration for HO if a sum of strength of all cells of the first target configuration is greater than a sum of strengths of all cells of the second target configuration at a particular instance. The sum of strengths of cells is evaluated in this example after a first condition of an A3 event is met to ensure that all cells in the target configuration can communicate with the UE.

In other example embodiments, the source cell may instruct the UE in the CHO command to evaluate an A3 event and another measure such as a missed-discovery reference signal (DRS)-count (for NR-unlicensed). If A3 events occur for both a first target configuration and a second target configuration, the UE is instructed to select a target configuration based on missed DRS counts for PCells of the first and second target configurations, respectively. If the missed DRS count for the PCell of the first target configuration is less than the missed DRS count for the PCell of the second target configuration, the UE selects the PCell of the first target configuration for handover.

<FIG> illustrates an example embodiment of a node, such as a gNB.

As shown, the gNB includes: a memory <NUM>; a processor <NUM> connected to the memory <NUM>; various interfaces <NUM> connected to the processor <NUM>; and one or more antennas or antenna panels <NUM> connected to the various interfaces <NUM>. The various interfaces <NUM> and the antenna <NUM> may constitute a transceiver for transmitting/receiving data to/from a UE via a plurality of wireless beams or to/from one or more TRPs. As will be appreciated, depending on the implementation of the gNB, the gNB may include many more components than those shown in <FIG>. However, it is not necessary that all of these generally conventional components be shown in order to disclose the illustrative example embodiment.

The memory <NUM> may be a computer readable storage medium that generally includes a random access memory (RAM), read only memory (ROM), and/or a permanent mass storage device, such as a disk drive. The memory <NUM> also stores an operating system and any other routines/modules/applications for providing the functionalities of the node (e.g., functionalities of a node, methods according to example embodiments, etc.) to be executed by the processor <NUM>. These software components may also be loaded from a separate computer readable storage medium into the memory <NUM> using a drive mechanism (not shown). Such separate computer readable storage medium may include a disc, tape, DVD/CD-ROM drive, memory card, or other like computer readable storage medium (not shown). In some example embodiments, software components may be loaded into the memory <NUM> via one of the various interfaces <NUM>, rather than via a computer readable storage medium.

The processor <NUM> may be configured to carry out instructions of a computer program by performing the arithmetical, logical, and input/output operations of the system. Instructions may be provided to the processor <NUM> by the memory <NUM>.

The various interfaces <NUM> may include components that interface the processor <NUM> with the antenna <NUM>, or other input/output components. As will be understood, the various interfaces <NUM> and programs stored in the memory <NUM> to set forth the special purpose functionalities of the node will vary depending on the implementation of the node.

The interfaces <NUM> may also include one or more user input devices (e.g., a keyboard, a keypad, a mouse, or the like) and user output devices (e.g., a display, a speaker, or the like).

Although not specifically discussed herein, the configuration shown in <FIG> may be utilized to implement, inter alia, TRPs, gNBs, other radio access and backhaul network elements, Central Units (CUs), eNBs, ng-eNBs, or the like. In this regard, for example, the memory <NUM> may store an operating system and any other routines/modules/applications for providing the functionalities of the TRPs, gNBs, etc. (e.g., functionalities of these elements, methods according to the example embodiments, etc.) to be executed by the processor <NUM>.

<FIG> illustrates an example embodiment of a user equipment (UE).

As shown, the UE includes: a memory <NUM>; a processor <NUM> connected to the memory <NUM>; various interfaces <NUM> connected to the processor <NUM>; and one or more antennas or antenna panels <NUM> connected to the various interfaces <NUM>. The various interfaces <NUM> and the antenna <NUM> may constitute a transceiver for transmitting/receiving data to/from a network node via a plurality of wireless beams. As will be appreciated, depending on the implementation of the UE, the UE may include many more components than those shown in <FIG>. However, it is not necessary that all of these generally conventional components be shown in order to disclose the illustrative example embodiment.

The memory <NUM> may be a computer readable storage medium that generally includes a random access memory (RAM), read only memory (ROM), and/or a permanent mass storage device, such as a disk drive. The memory <NUM> also stores an operating system and any other routines/modules/applications for providing the functionalities of the UE (e.g., functionalities of a UE, methods according to example embodiments, etc.) to be executed by the processor <NUM>. These software components may also be loaded from a separate computer readable storage medium into the memory <NUM> using a drive mechanism (not shown). Such separate computer readable storage medium may include a disc, tape, DVD/CD-ROM drive, memory card, or other like computer readable storage medium (not shown). In some example embodiments, software components may be loaded into the memory <NUM> via one of the various interfaces <NUM>, rather than via a computer readable storage medium.

As discussed herein, illustrative embodiments will be described with reference to acts and symbolic representations of operations (e.g., in the form of flow charts, flow diagrams, data flow diagrams, structure diagrams, block diagrams, etc.) that may be implemented as program modules or functional processes include routines, programs, objects, components, data structures, etc., that perform particular tasks or implement particular abstract data types and may be implemented using existing hardware at, for example, existing user equipment, base stations, eNBs, RRHs, gNBs, femto base stations, network controllers, computers, Central Units (CUs), ng-eNBs, WLAN access points (AP), WLAN stations (STA), other radio access or backhaul network elements, or the like. Such existing hardware may be processing or control circuitry such as, but not limited to, one or more processors, one or more Central Processing Units (CPUs), one or more controllers, one or more arithmetic logic units (ALUs), one or more digital signal processors (DSPs), one or more microcomputers, one or more field programmable gate arrays (FPGAs), one or more System-on-Chips (SoCs), one or more programmable logic units (PLUs), one or more microprocessors, one or more Application Specific Integrated Circuits (ASICs), or any other device or devices capable of responding to and executing instructions in a defined manner.

As disclosed herein, the term "storage medium," "computer readable storage medium" or "non-transitory computer readable storage medium" may represent one or more devices for storing data, including read only memory (ROM), random access memory (RAM), magnetic RAM, core memory, magnetic disk storage mediums, optical storage mediums, flash memory devices and/or other tangible machine-readable mediums for storing information. The term "computer-readable medium" may include, but is not limited to, portable or fixed storage devices, optical storage devices, and various other mediums capable of storing, containing or carrying instruction(s) and/or data.

Furthermore, example embodiments may be implemented by hardware, software, firmware, middleware, microcode, hardware description languages, or any combination thereof. When implemented in software, firmware, middleware or microcode, the program code or code segments to perform the necessary tasks may be stored in a machine or computer readable medium such as a computer readable storage medium. When implemented in software, a processor or processors will perform the necessary tasks. For example, as mentioned above, according to one or more example embodiments, at least one memory may include or store computer program code, and the at least one memory and the computer program code may be configured to, with at least one processor, cause a network element or network device to perform the necessary tasks. Additionally, the processor, memory and example algorithms, encoded as computer program code, serve as means for providing or causing performance of operations discussed herein.

A code segment of computer program code may represent a procedure, function, subprogram, program, routine, subroutine, module, software package, class, or any combination of instructions, data structures or program statements. A code segment may be coupled to another code segment or a hardware circuit by passing and/or receiving information, data, arguments, parameters or memory contents. Information, arguments, parameters, data, etc. may be passed, forwarded, or transmitted via any suitable technique including memory sharing, message passing, token passing, network transmission, etc..

The terms "including" and/or "having," as used herein, are defined as comprising (i.e., open language). The term "coupled," as used herein, is defined as connected, although not necessarily directly, and not necessarily mechanically. Terminology derived from the word "indicating" (e.g., "indicates" and "indication") is intended to encompass all the various techniques available for communicating or referencing the object/information being indicated. Some, but not all, examples of techniques available for communicating or referencing the object/information being indicated include the conveyance of the object/information being indicated, the conveyance of an identifier of the object/information being indicated, the conveyance of information used to generate the object/information being indicated, the conveyance of some part or portion of the object/information being indicated, the conveyance of some derivation of the object/information being indicated, and the conveyance of some symbol representing the object/information being indicated.

Claim 1:
A user equipment comprising:
at least one processor; and
at least one memory including computer program code, the at least one memory and the computer program code configured to, with the at least one processor, cause the user equipment to
obtain a conditional handover command, the conditional handover command indicating a multiple cell target for handover from a source cell and at least one performance margin, each of the at least one performance margin associated with a cell neighboring a first cell in the multiple cell target,
determine whether to initiate a handover to the first cell based on the at least one performance margin, and
transmit data to the first cell based on the determination of whether to initiate the handover,
wherein the at least one performance margin is either a permitted signal offset for a first frequency or a permitted difference between a measured signal strength of the first cell and a measured signal strength of the cell neighboring the first cell.