Handover between nodes using different radio access technologies

Abstract

The invention relates to handover between nodes using different radio access technologies. An apparatus is configured to operate in a mode that causes the apparatus to communicate with a first node and a second node using different radio access technologies (RAT). The apparatus is configured to: respond to receiving conditional handover information from a first node, the conditional handover information comprising configuration information for a second node and a core network indication indicating whether the first node and the second node provide access to a same, compatible or incompatible core network; determining whether at least one switching condition is satisfied; and generating, in a case where the at least one handover condition is satisfied, a handover confirmation report including an indication of the at least one handover condition determined to be satisfied; sending a report to the second node; and performing a handover such that the device is no longer connected to the first node and the device is connected to the second node.

Description

Technical Field

[0001] The various example embodiments relate to mobile communication networks, and in particular embodiments involve handover between nodes operating using different Radio Access Technologies (RATs). Background Technology

[0002] Inter-RAT handover can lead to a lack of continuity in user plane data. That is, core network routes are updated, but data loss may occur during the creation of a new UE context in the target RAT because it is not possible to use the UE context from the previous source RAT. Summary of the Invention

[0003] The scope of protection sought for the various exemplary embodiments of this disclosure is set forth in the independent claims. Exemplary embodiments and features (if any) described herein that do not fall within the scope of the independent claims are to be construed as examples useful for understanding the various embodiments of the invention.

[0004] According to various, but not necessarily all, example embodiments of this disclosure, an apparatus is provided, comprising: at least one processor; and at least one memory storing instructions, which, when executed by the at least one processor, cause the apparatus to at least: operate in a mode causing the apparatus to communicate with a first node and a second node using different Radio Access Technologies (RATs); respond to receiving conditional handover information from the first node, the conditional handover information including: configuration information for the second node, and a core network indication regarding whether the first node and the second node provide access to one of the following: the same core network, or different core networks that are compatible with each other, or different core networks that are incompatible with each other; determine whether at least one handover condition is satisfied; and when at least one handover condition is satisfied, initiate a handover process by: generating a handover confirmation report, the handover confirmation report including: an indication of the at least one handover condition determined to be satisfied; sending the report to the second node; and performing the handover such that the apparatus is no longer connected to the first node and the apparatus is connected to the second node.

[0005] Recognizing that in situations where devices such as user equipment are simultaneously connected to two network nodes operating using different radio access technologies, a conditional handover connecting only to the other node can be an efficient way to perform a handover when the device moves out of the radio coverage of one cell in the cell of one node, and that this handover can be performed by providing the user equipment with configuration information along with core network compatibility or other indications before the handover, with no or very little data loss, and with no or at least reduced interruption. Core network compatibility determines whether certain configurations can be reused, derived, or whether they need to be regenerated. A compatible core network is one in which many architectural aspects, configurations, and functions are identical or similar, allowing for continuity of user plane data during handover, enabling data packets to be retained rather than dropped, and allowing the derivation of security keys for moving from one RAT to another to be defined and signaled. It is also recognized that the conditions triggering the handover are known to the device rather than the network, and that sending this information in the handover confirmation report can improve the process.

[0006] Further specific and preferred aspects are set forth in the appended independent and dependent claims. Features of the dependent claims may be suitably combined with features of the independent claims, and in a manner different from those expressly set forth in the claims.

[0007] When a device feature is described as operable to provide a function, it will be understood that this includes device features that provide that function, or are adapted to or configured to provide that function. Attached Figure Description

[0008] Some exemplary embodiments will now be described with reference to the accompanying drawings, in which:

[0009] Figure 1 The illustration shows the principle of conditional handover from UE 6G-5G dual connectivity to 5G connectivity according to an example embodiment;

[0010] Figure 2 The diagram illustrates a signaling flowchart for conditional handover between RATs according to an embodiment.

[0011] Figure 3 A user equipment within a network according to an embodiment is schematically shown;

[0012] Figure 4 A flowchart illustrating, schematically, the steps of a method performed at a user equipment according to an embodiment is shown;

[0013] Figure 5 A flowchart illustrating schematically the steps of a method performed at a 6G node according to an embodiment is shown; and

[0014] Figure 6 A flowchart illustrating, schematically demonstrating, the steps of a method performed at a 5G node according to an embodiment is shown. Detailed Implementation

[0015] Before discussing the example embodiments in more detail, an overview will first be provided.

[0016] The implementation proposes using the Conditional Handover (CHO) principle for inter-system handover, to switch between RATs, such as from 6G-5G dual connectivity operation to 5G-only operation.

[0017] Conditional handover was introduced in 3GPP Release 16 (for both LTE and NR in-process handover). Its primary purpose was to improve the reliability of the handover process (because the HO command itself can be sent under good radio conditions, while HO triggering often occurs when radio conditions toward the current source cell are less reliable). It also reduces downtime for in-system handovers by avoiding additional steps in the HO process.

[0018] Multiple RAT Spectrum Sharing (MRSS) has been discussed as an enabler for 6G deployment, where the same site is shared by both 5G and 6G cells (potentially at the HW level, so that the same "cell" actually handles both 5G and 6G transmissions and receptions). This allows operators to deploy 6G and 5G on the same frequency band.

[0019] The embodiments attempt to allow for advance preparation for a handover to be performed. In the case of dual connectivity, the embodiments leverage the fact that a connection between the User Equipment (UE) and the Network NW (NW) for the target node has already been established, since the UE is already operating on the new 5G target carrier as a secondary cell, while anchored on the 6G carrier. The handover occurs when the 6G signal weakens and therefore the UE switches to the 5G cell, which then becomes the anchor cell.

[0020] User equipment can be any mobile terminal or terminal device capable of wireless communication. By way of example and not limitation, user equipment (UE) can also be referred to as communication equipment, terminal equipment, or mobile station (MS). User equipment can include, but is not limited to, mobile phones, cellular phones, smartphones, tablets, wearable terminal devices, personal digital assistants (PDAs), in-vehicle wireless terminal devices, and smart devices.

[0021] While the embodiments address the multi-RAT dual connectivity scenario, they are also applicable to multi-SIM (Subscriber Identity Module) scenarios where the UE is simultaneously connected to, for example, both 5G and 6G. In these cases, if 6G becomes weak and 5G connectivity becomes available, the UE can switch to that connection if permitted by multiple MUSIM configurations (e.g., network configuration switching and both 5G and 6G use the same operator).

[0022] Figure 1 This illustration demonstrates how UE 10 operates under dual connectivity and is connected to both 5G base transceiver stations BTS 20 and 6G BTS 22 to increase data rates. In this embodiment, the core network 50 is identical for both BTS 20 and 22, and the 6G node 20 is the anchor and master node, thus controlling any handovers, while the 5G BTS 22 is the secondary node. The master node 20 configures the UE with a conditional handover configuration (CHO) for switching to 5G-only operation.

[0023] Then, UE 10 will determine whether the CHO condition is met, and if so, this results in the generation and transmission of a CHO confirmation message to 5G BTS 20, the current secondary node providing radio coverage for UE 10 in the secondary cell. In response, 5G node 20 will send a 5G signaling connection initiation. The 5G 22BTS and 6G 20BTS will exchange previously exchanged information regarding UE configuration and security keys. This signaling... Figure 2 It is shown in more detail in the middle.

[0024] Figure 2 An example signaling diagram between UE 10 and 5G and 6G nodes 22 and 20 during a CHO is shown. Two embodiments are disclosed below. In one embodiment, the UE switches from a dual-connectivity state in which the UE is simultaneously connected to both 5G and 6G nodes (the 6G node being the anchor node) to a state in which the UE is connected only to the 5G node (so that the 5G node subsequently needs to be switched to act as the anchor node). In another embodiment, UE 10 is a multi-SIM UE, with one SIM providing connectivity to the 5G node and the other SIM providing connectivity to the 6G node. If the 6G node signal weakens and UE 10 can no longer reliably connect to the 6G cell, UE 10 performs a handover to connect only to the 5G cell.

[0025] Dual connectivity implementation example:

[0026] 1) The master node 20, used in 6G-5G dual connectivity (or typically for aggregation) embodiments, configures the UE with a CHO configuration for 5G-only operation. This configuration may also indicate whether the CN is the same (or compatible) for the two RATs.

[0027] 2) The UE can send a report to the 6G node (master node) 20 indicating that it is connected to two nodes, or in this embodiment, the node may not send a report when it knows this.

[0028] 3) Then, 6G node 20 sends an inter-RAT CHO request, which specifies that inter-RAT handover should be supported for the UE identified by the UE ID in the request. 6G node 20 also sends information about the UE's security key. This may include information on how the security key is derived.

[0029] 4) The 5G node (secondary node) 22 responds using an ACK, which indicates whether the RAT-to-5G CHECK is permitted for the UE with that identifier. It can also send information about the security key, such as how it is derived from the root key, and it can send an indication of the UE's identifier when communicating with the 5G node 22. If the 5G node and 6G node are not co-located, it can send an indication that a timing advance is required, or an indication of the value applied to the timing advance. If they are co-located, it can send an indication that the TA and synchronization information can be retained and reused.

[0030] 5) The 6G node 20 responds by sending a CHO configuration message for inter-RAT handover to the UE. This includes an indication of whether the core network is the same or different for the two nodes, and if the core networks are different for the two nodes, the indication can also indicate whether the different core networks are compatible or incompatible for the two nodes. The CHO configuration message may include an indication of whether the UE should retain or discard at least a portion of the stored data in the protocol stack, and it may also provide security key derivation information that allows the UE to derive a security key for communicating with the 5G node when the 5G node becomes the anchor node. Whether the UE should retain or discard at least a portion of the stored data in the protocol stack, and whether it can derive the security key from the information received in the CHO configuration message, will depend on whether the core networks are the same or compatible. Depending on this, one or more indications can be sent to the user equipment indicating whether the core networks are compatible or incompatible, and indicating the behavior of the user equipment during the handover process. For example, protocol stack-related behavior can be directly indicated or determined by the UE based on the indication regarding core network compatibility.

[0031] 6) A CHO is triggered when one or more of the following conditions are met at the UE (based on network configuration, see step 1):

[0032] - The UE is considered to have lost synchronization with the 6G carrier, for example, the maximum number of Radio Link Control (RLC) retransmissions were triggered for uplink UL control plane signaling (meaning the UE no longer provides control plane signaling to the 6G base station and will typically trigger an RLF radio link failure for the UE).

[0033] - The measured 6G signal is below the configured threshold (similar to an A2 event), optionally within a certain period of time (i.e., the trigger period or the TTT time of N measurements).

[0034] - The packet error rate (in L1 or L2) exceeds a threshold on the configured observation window (e.g., an X ms window with a Y% packet error rate); and in some embodiments: the UE will also perform at least one of the following:

[0035] Check UP RLC retransmission - if the maximum retransmission has not been reached, proceed with the next action; otherwise, trigger a CHO.

[0036] Perform additional control plane (CP) or user plane (UP) transfers to check link status (e.g., L1 transfers with uplink pseudo-data for TB transmit buffers, BSR / PHR, or other MAC CEs), and then perform only CHO.

[0037] When the UE determines that one or more CHO conditions are met, the UE executes a CHO toward the target RAT. If the CHO request indicates that the core network (CN) is the same or compatible for both RATs, the UE derives a new security key for the target RAT from the information received from the 6G node in the CHO configuration message, and triggers retransmission of all cached PDCP (Packet Data Convergence Protocol) SDUs (Serving Data Units) to ensure no loss of data continuity in the user plane. If the CHO request indicates that the core network data continuity is different and incompatible for the user plane, the UE derives a new security key based on the target RAT key derivation rules and discards the cached PDCP SDUs.

[0038] In some embodiments, the UE can slow down the handover based on how mobility has worked previously; for example, if the UE has already done a lot of ping-pong, it will not trigger a handover soon. This can be done by updating some thresholds for triggering a CHO to higher required values, or by requiring more than one threshold to trigger a CHO.

[0039] 7) The UE will apply the user plane procedure to the RAT-inter-CHO application.

[0040] Sometime after step 4 and before step 8, step signaling step 4a will occur, in which the 6G node source node 20 will forward cached data that has not yet been acknowledged as received to the 5G node 22. This is forwarded as an unencrypted PDCP packet.

[0041] 8) The UE will send a CHO acknowledgment to the 5G node 22, indicating that the UE is no longer connected to the 6G node 20. This message may also include the UE identifier. In some embodiments, the message may also include UP routing information to allow the RAN to avoid data loss, for example, by utilizing data forwarding based on the provided UP routing information. Furthermore, in some cases, the triggering conditions for the CHO allow the source / target RAN to determine the reason for triggering the CHO, for example, in the presence of multiple conditions. The UE may also indicate whether it has adjusted the CHO conditions and how it has adjusted them.

[0042] After receiving the CHO execution confirmation from the UE, the network will take appropriate action to reroute the user plane to the new RAT connection.

[0043] With the same evolved 5G core at its core, data routing updates can also be rapid. Therefore, this switching execution time can be very fast, with short interruptions in the data stream.

[0044] Dual SIM Implementation

[0045] 1) The UE is connected to both a 5G node via one SIM and a 6G node via another SIM. The UE is configured with a CHO configuration for 5G-only operation. This configuration can also specify whether the CN is the same (or compatible) for both RATs.

[0046] 2) The UE sends a report to the 6G node 20, indicating that the UE is connected to both the 5G node and the 6G node.

[0047] 3) Then, 6G node 20 sends an inter-RAT CHO request, which specifies that inter-RAT handover should be supported for the UE identified by the UEID. 6G node 20 also sends information about the UE's security key. This may include information about the 6G SIM number, which is used to derive the security key.

[0048] 4) The 5G node responds with an ACK, which indicates that the RAT-to-5G CHO can be used for the UE with that identifier. It can also send information about the security key, such as how to derive the key from it, and it can send an indication of the UE identifier used to communicate with the 5G node. In cases where the 5G and 6G nodes are not co-located, it can send updated synchronization and timing advance TA information to the 5G node.

[0049] 5) The 6G node 20 responds to the CHO configuration required for inter-RAT handover. This may optionally include an indication of the inter-RAT HO information that should be included in the CHO confirmation message. The CHO configuration may include an indication of whether the UE should retain or discard at least a portion of the stored data in the protocol stack, and it also provides security key derivation information that allows the UE to derive a security key for communicating with the 5G node.

[0050] 6) CHO is triggered when one or more conditions for the dual connectivity case are met.

[0051] When the UE determines that one or more CHO conditions are met, the UE executes a CHO toward the target RAT. If the CHO indicates that the CN is the same or compatible for both RATs, the UE derives a new security key for the target RAT from the received information and triggers retransmission of all PDCP (Packet Data Convergence Protocol) SDUs (Serving Data Units) in the cache, ensuring no data or continuity loss in the user plane. If the core network is identified as different and incompatible, the UE derives a new security key based on the target RAT key derivation rules and discards the cached PDCP SDUs.

[0052] In some embodiments, the UE can slow down the handover based on how well previous mobility has worked; for example, if the UE has already performed many ping-pongs, it will not trigger a handover soon. This can be done by updating some thresholds for triggering a CHO based on a higher required signal quality value, or by requiring more than one threshold to trigger a CHO.

[0053] 7) The UE will apply the user plane procedure for the RAT-to-CHO, which means that the mapping data stream is now active.

[0054] Sometime after step 4 and before step 8, signaling step 4a occurs, in which source node 20 forwards buffered data (UL / DL uplink / downlink) that has not yet been acknowledged as received to destination node 22. This is forwarded as an unencrypted PDCP packet.

[0055] 8) The UE will send a CHO acknowledgment to 5G node 22, indicating that the UE is no longer connected to node 20. This message may also include the UE identifier. In some embodiments, the message may also include UP user plane routing information to allow the RAN radio access network to avoid data loss, for example, by utilizing data forwarding based on the provided UP routing information. Furthermore, in some cases, the triggering conditions for the CHO allow the source / target RAN to determine the reason for triggering the CHO, for example, in the presence of multiple conditions. The UE may also indicate whether it has adjusted the CHO conditions and how it has adjusted them.

[0056] 9) After receiving the CHO execution confirmation from the UE, the 5G node will apply user plane routing.

[0057] The network will take appropriate action to reroute the user plane to the new RAT connection. At this point, the target 5G node 22 can request a path switch from the AMF in the core network, and the AMF can send an "end marker" packet to the source 6G node 22 to indicate the last data sent to the source cell. The AMF confirms the path switch and reroutes the data to the 5G node's cell (i.e., the UPF user plane function will now send all data to the target cell).

[0058] When the core is the same evolved 5G core or a compatible core network, updates to data routes can be rapid. Therefore, this handover execution time can be very fast, with short interruptions in the data stream.

[0059] Security Key Derivation

[0060] As described above, when the core network is identical or compatible, the security key can be derived from the previous security key, and the information allowing this to happen is first provided in message 3, namely the inter-RAT CHO request from 6G node 20 to 5G node 22, which indicates that the security key should be reused, and in message 4, the CHO request ack from 5G node 22 to 6G node (which contains information about how to derive the key from the current key) can be provided. This information is then sent to user equipment 10 in message 5 in the CHO configuration for inter-RAT handover messages.

[0061] When the core networks are compatible or identical, the derivation of the security key can follow the procedures outlined below. These are based on the procedures used for handover, where the RAT remains unchanged and the cell and UE can derive the key from the previous key. Typically, when an inter-RAT handover occurs and the RAT changes, the derivation of the security key always reverts to the original USIM key, and in effect, the UE and (multiple) target cells regenerate the security key from scratch. Implementations recognize that when the core networks are compatible or identical, the security key can be derived from the previous key, allowing signaling notification between the node and the UE, and providing user plane data continuity and reducing any interruptions.

[0062] The focus is on how the security key is derived when the UE is connected to the serving cell, using the "NH" (next-hop) key from the cell-only AMF key (K). AMF Derive the "per cell" security key (i.e., K) NG-RANThis forms the basis for all other keys used for the UE in that cell. This means there exists a "root key" used to derive those (i.e., the key value from K using the NH key value). AMF The derived K gNB It is based on information stored in the SIM card.

[0063] When the cell used for handover changes, where the RAT remains the same (i.e., the RAT does not change), there are typically two options for deriving the security key used for the UE:

[0064] a. "Root Key" (i.e., K) gNB The new NH key has been changed, which also means that the "per-cell" security key (i.e., K) is also changed. NG-RAN Also changed (and from K) NG-RAN Any derived keys (such as CP and UP keys) are also changed. This is communicated to the UE by the target cell requesting the UE to derive the new key, and the target cell also derives the new key using the same key derivation algorithm.

[0065] b. Per-cell UE security key (i.e., K) UPenc K UPint K RRCint K RRCenc The NCC value (i.e., the counter value added to the key derivation algorithm) is re-derived from the root key. This NCC value does not affect the "root key" but creates a new per-cell key for the UE. This is communicated to the UE by providing the new NCC value.

[0066] In the case of RAT changes, traditionally for such inter-RAT HOs, key derivation always reverts to the USIM key, meaning the UE re-performs the entire key derivation process from scratch, similar to connection establishment. Alternative implementations propose the reuse of NH / NCC-based key derivation, which allows user plane data continuity by simultaneously applying forwarded data. This is typically not performed in inter-RAT HOs because the UP architectures in different RATs are so different that it is too difficult, and the key derivation and / or key hierarchy structures between RATs are usually different. However, it has been recognized that this becomes possible when the same or similar / compatible CNs exist in both 5G and 6G.

[0067] Figure 3 User equipment 10 according to an embodiment is shown. User equipment 10 includes a processor 18, a data storage 12 for storing data and program code, one or more SIM cards 17, and a receiving and transmitting circuitry 16. In this embodiment, user equipment 10 is connected to both a 6G network node 20 and a 5G network node 22 in a dual connectivity mode, such that the 6G node 20 is the anchor node and the 5G node 22 is the secondary node.

[0068] The 6G node 20 includes a data storage device 42 for storing data and program code, a processor 44, and a receiving and transmitting circuitry system 46. The 6G network node 20 provides 6G radio coverage within the cell 30.

[0069] Network node 22 is a 5G network node and includes: a data storage 45, a processor 43 for executing computer code stored in the data storage 45, and a receiving and transmitting circuitry 41. Network node 22 provides radio coverage within 5G cell 32, which has a larger coverage area than 6G cell 30. Figure 3 The core network 50 is also schematically shown, which is the same for both 5G node 22 and 6G node 20 in this embodiment.

[0070] UE 10 is moving, and at some point it will exit the radio coverage provided by 6G cell 30 and enter the radio coverage provided only by 5G cell 32. User equipment 10 is configured to determine, based on detected radio conditions, when a conditional handover should be performed, and when to switch from 6G node 20 to 5G node 22, making the 5G node the anchor node. About Figure 2 The signaling that is executed to implement the switch is described.

[0071] Figure 4 A flowchart illustrating the steps of a method performed at a user equipment according to an embodiment is shown. In the initial step S10, the user equipment is connected to both the 5G node and the 6G node, and receives information from the 6G node regarding the conditions for a conditional switch to be triggered.

[0072] In some embodiments, when the UE is connected to a node in a multi-SIM embodiment (rather than a dual-connectivity embodiment), it can send an indication to the 6G node to indicate that it is connected to both the 5G node and the 6G node.

[0073] At step S20, the user equipment receives configuration information for inter-RAT handover, which includes an indication of whether the core network is the same or compatible for the two nodes. This indication determines the UE's behavior regarding the derivation of security keys and the retention or discarding of data. In some cases, as part of providing core network indication, the configuration information may include information explicitly indicating whether to retain or discard at least a portion of the stored data within the protocol stack, and / or information about how to derive the security key to be used in the target RAT. Then at D5, it is determined whether the UE has performed several handovers within a predetermined time period; in other words, whether multiple ping-pongs exist. If this is determined, at step S30, the conditions for conditional handover to be triggered can be updated to make them more difficult to satisfy, and thus attempt to avoid these ping-pongs. If not, at D15, it is determined whether the conditional handover conditions are satisfied. If they are, then at D25, it is determined whether the UE's mobility is very low. If not, at S50, the user plane procedures for inter-RAT handover are applied. That is, if the configuration information received in step S20 indicates that at least some data in the protocol stack should be retained, at least some data in the protocol stack is retained, where for example, the core network is specified as the same or compatible, or if not, at least some data in the protocol stack is discarded.

[0074] If mobility is determined to be very low, step S40, which involves waiting for a predetermined delay, is performed before step S50. This allows the handover to be delayed, where the detected deterioration in radio conditions is clearly not due to UE mobility and therefore may not continue to worsen. At step S60, a handover confirmation is sent to the 5G node, which includes the UE identifier and an indication of the handover trigger, and in some cases, this indication is also included if the conditions for the handover have been updated.

[0075] Figure 5 The steps in the method performed at the 6G node are shown. At step S100, an indication that the UE is also connected to the 5G node can be received. In some cases, this may not be received when the 6G node already knows this, such as in the case of dual connectivity.

[0076] In step S110, the 6G node generates an inter-RAT conditional handover request, which identifies the relevant UE and provides information about the UE's security key. In step S120, a conditional handover request acknowledgment is received, which includes information about how the security key can be derived, and indications regarding timing advance and synchronization for the 5G node. At this point, if the 6G and 5G nodes are co-located, this can simply be an indication that no update is needed; however, if they are not co-located, this could be an indication that timing advance needs to be acquired, or an indication of the value applied to the timing advance.

[0077] In step S130, the 6G node sends an inter-RAT conditional handover request to the user equipment, and the request includes one or more of the following: indications regarding whether the core networks are identical, compatible, or different; configuration information regarding the retention or discarding of at least some data in the protocol stack; and information regarding how the security key can be derived. In this respect, if the user plane configuration is to be retained—that is, if the core networks are identical or compatible for both nodes—this information indicates that at least some data in the protocol stack should be retained, while if the core networks are different, this data can be discarded.

[0078] In step S140, cached data within the 6G node that has not yet been acknowledged as received, received from or to be sent to the user equipment, is sent to the 5G node in unencrypted form.

[0079] Figure 6 The steps of a method performed at a 5G node according to an embodiment are illustrated. In the initial step S200, the 5G node receives an inter-RAT CHO request, which identifies the associated UE and includes information about a security key used by the 6G node to communicate with the user equipment. In step S210, the 5G node responds to the 6G node with an ACK, which includes a UE identifier for communicating with the 5G node, information for deriving the security key, and indications for timing advance TA and synchronization. At this point, it could be an indication that the TA and synchronization should be retained in the case of co-location of the 6G and 5G nodes, or it could be an indication that timing advance needs to be acquired, or an indication of a value applied to the timing advance. In step S215, the 5G node receives unencrypted data from the 6G node and adds it to its buffer.

[0080] At step S220, the 5G node receives a conditional handover confirmation message from the user equipment, which includes the user equipment identifier, an indication of the handover trigger, and any updates to the possible handover conditions. At step S230, it applies user plane routing for the data, and at step S240, it can forward any information regarding the handover trigger and updates to the handover conditions to the 6G node. It will also derive and apply an updated security key based on the configuration information received in the conditional handover request message.

[0081] The key advantage of using the above embodiments is that the handover is performed very quickly, and with this method, the 6G connection does not need to be dropped in advance if there is a possibility that it may deteriorate, because the conditional handover (CHO) allows the UE to move to the 5G node when it no longer needs to obtain messages via the 6G connection (as in the case of a regular inter-system handover).

[0082] The following describes the various aspects and embodiments:

[0083] According to various, but not necessarily all, example embodiments of this disclosure, an apparatus is provided, the apparatus including at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus to at least: operate in a mode causing the apparatus to communicate with a first node and a second node using different Radio Access Technologies (RATs); respond to receiving conditional handover information from the first node, the conditional handover information including configuration information for the second node and a core network indication indicating whether the first node and the second node provide access to one of the following: the same core network, different core networks that are compatible with each other, or different core networks that are incompatible with each other; determine whether at least one handover condition is met; and perform a handover if at least one handover condition is met, such that the apparatus is no longer connected to the first node and the apparatus is connected to the second node.

[0084] It has been recognized that in situations where a user equipment (UE) is connected to two network nodes and may move out of the radio coverage of one of the cells, conditional handover to connect only to the other cell can be performed efficiently by providing the UE with configuration information and an indication of the core network status before the handover (as this determines whether certain configurations can be reused, modified, or need to be regenerated), without data loss or with reduced data loss and without interruption or with at least reduced interruption. A compatible core network is one in which many architectural aspects, configurations, and functions are identical or similar, allowing for continuity of user plane data during handover, enabling data packets to be retained rather than dropped, and allowing security key derivations for moving from one RAT to another to be defined and signaled.

[0085] In some embodiments, the device is configured to operate in a mode comprising a dual connectivity mode, wherein the first node acts as an anchor node for the device and the second node acts as an auxiliary node; and after the switching, the second node acts as the anchor node for the device.

[0086] In other embodiments, the device is configured to operate with a plurality of subscriber identification modules (SIMs), a first SIM for communicating with a first radio access technology of the first node, and a second SIM for communicating with a second radio access technology of the second node.

[0087] In some embodiments where the device is configured to operate with multiple SIMs, the device is also configured to: generate a report indicating that the device is connected to both the first node and the second node; and send the report to the first node. When the device is configured to operate in dual connectivity mode, the first node knows that the device is also connected to the second node, and this does not require signaling.

[0088] In some embodiments, the first node operates at a higher frequency band than the second node. When the first node operates at a higher frequency than the second node, the radio coverage of the first node's cell may be less than that of the second node's cell, and therefore, a handover to the second node may be necessary. Therefore, such a handover can be planned in advance by providing the user equipment with configuration information for communicating with the second node prior to any handover.

[0089] In some embodiments, the first node includes a 6G node, and the second node includes a 5G node. For example, in dual connectivity, the 6G node would be the anchor node, but the 5G node can provide greater coverage, so the device can move out of the coverage area of ​​the 6G node, and the 5G node will need to become the anchor node.

[0090] In some embodiments, the apparatus is configured to: in response to a received core network indication indicating that the core network is the same or compatible for the first node and the second node, apply a user plane data routing procedure based on the configuration information received from the first node within the condition switching information.

[0091] Instructions regarding the core network allow devices to determine whether certain user plane data routing procedures can be applied that allow the retention of the topmost data layer and PDCP layer instead of discarding them. Retaining this data allows for user plane data continuity.

[0092] In some embodiments, the apparatus is configured to: derive a security key for the second node from the condition switching information, wherein the core network indication received from the first node indicates that the core network is the same or compatible for the first node and the second node.

[0093] Conditional handover CHO information may include indications of security keys, which could be information about the root key for dual connectivity scenarios or information about the second SIM for multi-SIM scenarios. This allows the device to derive keys from this information if the core network is identical or compatible with the two RATs. If the core network indication indicates core network incompatibility, the device needs to generate a security key based on the target RAT key derivation rules.

[0094] In some embodiments, in response to received configuration information indicating that the synchronization information and timing advance are to be reused, the apparatus is configured to retain the synchronization and timing advance configuration when performing the switch to the second node.

[0095] When the first and second nodes are co-located, the synchronization and timing advance will be the same for both nodes, and the device is provided with an indication of the synchronization and timing advance before switching, so that the device can retain and reuse the information when connecting to the second node.

[0096] In some embodiments, determining whether the at least one switching condition is met includes determining at least one of the following: whether uplink control signaling to the first node has triggered more than a predetermined number of retransmissions; whether the measured signal strength of the signal from the first node is lower than a configured threshold; whether the measured signal from the first node is lower than a configured threshold for a predetermined time; and whether the error rate in Layer 1 or Layer 2 during the predetermined time for which signaling is sent to the first node is higher than a predetermined threshold.

[0097] Since the device is configured to perform conditional switching, the conditions for triggering the switching can be determined at the device. Various indications of radio conditions, such as measured signal strength or signal failure, are compared to thresholds, and when they pass or equal the thresholds in a manner indicating poor radio conditions, this indicates that at least one switching condition is met, and the switching is triggered if a switching condition is required to trigger it. If more than one switching condition is required, the switching is triggered when one or more additional conditions are met.

[0098] In some embodiments, the step of performing the switching includes applying a user plane data routing procedure based on the configuration information received from the first node within the conditional switching information.

[0099] In some embodiments, the apparatus is further configured to generate a handover confirmation report for a transfer to the second node, the handover confirmation report indicating that the apparatus is no longer connected to the first node and including an identifier for the user equipment.

[0100] In some embodiments, the apparatus is configured to generate a handover confirmation report for transmission to the second node, the handover confirmation report including an indication of the at least one handover condition that triggered the handover.

[0101] In some embodiments, the apparatus includes user equipment.

[0102] According to various, but not necessarily all, example embodiments of this disclosure, a method is provided to be performed at a device, the method comprising: operating in a mode in which the device communicates with a first node and a second node using different Radio Access Technologies (RATs); receiving condition handover information from the first node, the condition handover information including: configuration information for the second node, and a core network indication indicating whether the first node and the second node provide access to one of the following: the same core network, different core networks that are compatible with each other, or different core networks that are incompatible with each other; determining whether at least one handover condition is satisfied; and performing a handover if at least one handover condition is satisfied, such that the device is no longer connected to the first node and the device is connected to the second node.

[0103] In some embodiments, the mode includes: a dual connectivity mode, wherein the first node acts as an anchor node for the device and the second node acts as an auxiliary node; and after the switch, the second node acts as the anchor node for the device.

[0104] In other embodiments, the device is configured to operate with a plurality of SIMs, a first SIM for communicating with a first radio access technology of the first node, and a second SIM for communicating with a second radio access technology of the second node.

[0105] In some embodiments where the device is configured to operate with multiple SIMs, the method includes: generating a report indicating that the device is connected to both a first node and a second node; and sending the report to the first node.

[0106] In some embodiments, the method includes: receiving a core network indication that the core network is the same or compatible with the first node and the second node, and applying a user plane data routing procedure based on the configuration information received from the first node within the condition switching information.

[0107] In some embodiments, the method includes: deriving a security key for the second node from the condition switching information and the core network indication received from the first node.

[0108] In some embodiments, the method includes: receiving configuration information indicating that the synchronization information and timing advance are to be reused, and retaining the synchronization and timing advance configuration when the switch is performed to the second node.

[0109] In some embodiments, the method includes determining whether the at least one switching condition is met by determining at least one of the following: whether uplink control signaling to the first node has triggered more than a predetermined number of retransmissions; whether the measured signal strength of the signal from the first node is lower than a configured threshold; whether the measured signal from the first node is lower than a configured threshold for a predetermined time; and whether the error rate in layer 1 or layer 2 during a predetermined time period for which signaling notification is sent to the first node is higher than a predetermined threshold.

[0110] In some embodiments, the step of performing the switching includes applying a user plane data routing procedure based on the configuration information received from the first node within the conditional switching information.

[0111] In some embodiments, the method includes generating a handover confirmation report for a transfer to the second node, the handover confirmation report indicating that the device is no longer connected to the first node and including an identifier for the user equipment.

[0112] In some embodiments, the method includes: generating a handover confirmation report for transmission to the second node, the handover confirmation report including an indication of the at least one handover condition that triggered the handover.

[0113] According to various, but not necessarily all, example embodiments of this disclosure, an apparatus is provided comprising: components for communicating with a first node and a second node using different Radio Access Technologies (RATs); components for receiving conditional handover information from the first node, the conditional handover information including configuration information for the second node and a core network indication indicating whether the first node and the second node provide access to one of the following: the same core network, different core networks that are compatible with each other, or different core networks that are incompatible with each other; components for determining whether at least one handover condition is met; and, if at least one handover condition is met, triggering components for performing a handover to perform the handover such that the apparatus is no longer connected to the first node and the apparatus is connected to the second node.

[0114] The apparatus may also include components for performing the optional features listed with respect to the above methods.

[0115] According to various, but not necessarily all, example embodiments of this disclosure, an apparatus is provided comprising: a circuit system configured to communicate with a first node and a second node using different Radio Access Technologies (RATs); a circuit system configured to receive conditional handover information from the first node, the conditional handover information including configuration information for the second node and a core network indication indicating whether the first node and the second node provide access to one of the following: the same core network, different core networks that are compatible with each other, or different core networks that are incompatible with each other; a circuit system configured to determine whether at least one handover condition is satisfied; and, if at least one handover condition is satisfied, triggering the circuit system configured to perform the handover to perform the handover such that the apparatus is no longer connected to the first node and the apparatus is connected to the second node.

[0116] The apparatus may also include a circuit system configured to perform the optional features listed with respect to the above methods.

[0117] According to various, but not necessarily all, example embodiments of this disclosure, a computer program including instructions is provided that, when executed by a device, causes the device to perform at least the following:

[0118] In a mode in which the device communicates with a first node and a second node using different Radio Access Technologies (RATs), the device responds to receiving conditional switching information from the first node, the conditional switching information including configuration information for the second node and a core network indication indicating whether the first node and the second node provide access to one of the following: the same core network, different core networks that are compatible with each other, or different core networks that are incompatible with each other.

[0119] Determine whether at least one switching condition is met; and if at least one switching condition is met, perform a switch such that the device is no longer connected to the first node and the device is connected to the second node.

[0120] According to various, but not necessarily all, example embodiments of this disclosure, a computer-readable medium including instructions that, when executed by an apparatus, cause the apparatus to perform at least the following: operate in a mode that causes the apparatus to communicate with a first node and a second node using different Radio Access Technologies (RATs); respond to receiving conditional switching information from the first node, the conditional switching information including configuration information for the second node; and a core network indication indicating whether the first node and the second node provide access to one of the following: the same core network, different core networks that are compatible with each other, or different core networks that are incompatible with each other;

[0121] Determine whether at least one switching condition is met; and if at least one switching condition is met, perform a switch such that the device is no longer connected to the first node and the device is connected to the second node.

[0122] According to various, but not necessarily all, example embodiments of this disclosure, a non-transient computer-readable medium is provided, comprising program instructions stored thereon for performing at least the following: causing a device to operate in a mode that enables the device to communicate with a first node and a second node using different Radio Access Technologies (RATs); responding to receiving conditional handover information from the first node, the conditional handover information including configuration information for the second node and a core network indication indicating whether the first node and the second node provide access to one of the following: the same core network, different core networks that are compatible with each other, or different core networks that are incompatible with each other; causing the device to determine whether at least one handover condition is met; and, if at least one handover condition is met, causing the device to perform a handover such that the device is no longer connected to the first node and the device is connected to the second node.

[0123] The instructions detailed above can be used to execute the optional features listed with respect to the methods described above.

[0124] According to various, but not necessarily all, example embodiments of this disclosure, an apparatus is provided for providing radio coverage to a user equipment according to a first radio access technology, the apparatus comprising:

[0125] At least one processor; and at least one memory storing instructions, which, when executed by the at least one processor, cause the device to perform at least the following:

[0126] The system provides radio coverage to the user equipment within the radio cell; determines that the user equipment also communicates with a second node using a second radio access technology; and generates a message for transmission to the user equipment, the message including conditional switching information, the conditional switching information including: configuration information for communicating with the second node, and a core network indication indicating whether the first node and the second node provide access to one of the following: the same core network, different core networks that are compatible with each other, or different core networks that are incompatible with each other.

[0127] User equipment behavior will depend on core network compatibility. Therefore, core network indicators will exist to provide indication of whether the core network is compatible or incompatible. In some cases, the core networks can be the same, in which case they will be compatible.

[0128] In some embodiments, the apparatus is configured to: provide radio coverage to the user equipment as an anchor node, and the second node provides radio coverage as an auxiliary node.

[0129] In some embodiments, the apparatus is further configured to generate a message for transmission to the second node, the message including configuration information for communicating with the user equipment.

[0130] In some embodiments, the message for transmission to the second node includes an inter-RAT condition switching request.

[0131] In some embodiments, the apparatus is further configured to receive condition switching information including the configuration information from the second node.

[0132] In some embodiments, the message includes information related to generating a security key for the user equipment for communication with the second node.

[0133] When the instruction indicates that the core network is the same or compatible, the security key information can be an indication of how the security key is derived from the received information.

[0134] In some embodiments, when the first node and the second node are co-located, the received configuration information includes an indication that the timing advance and synchronization information should be retained and does not need to be updated.

[0135] In some embodiments, when the first node and the second node are not co-located, the received configuration information includes: an indication that a timing advance needs to be obtained, or an indication of a value applied to the timing advance, for the user equipment to use to communicate with the second node.

[0136] In some embodiments, the message for transmission to the second node further includes an identifier that identifies the user equipment.

[0137] In some embodiments, the device includes a 6G base station.

[0138] According to various, but not necessarily all, example embodiments of this disclosure, a method is provided for providing radio coverage to a user equipment according to a first radio access technology, the method comprising: providing the radio coverage to the user equipment within a radio cell; determining that the user equipment also communicates with a second node using a second radio access technology; and generating a message for transmission to the user equipment, the message including conditional switching information, the conditional switching information including configuration information for communicating with the second node, and a core network indication indicating whether the first node and the second node provide access to one of the following: the same core network, different core networks that are compatible with each other, or different core networks that are incompatible with each other.

[0139] In some embodiments, the method includes: providing radio coverage to the user equipment as an anchor node, and the second node providing radio coverage as an auxiliary node.

[0140] In some embodiments, the method includes: generating a message for transmission to the second node, the message including configuration information for communicating with the user equipment.

[0141] In some embodiments, the message for transmission to the second node includes an inter-RAT condition switching request.

[0142] In some embodiments, the method includes: receiving condition switching information including the configuration information from the second node.

[0143] According to various, but not necessarily all, example embodiments of this disclosure, an apparatus is provided comprising: components for providing radio coverage to a user equipment according to a first radio access technology, the apparatus including: components for providing the radio coverage to the user equipment within a radio cell; components for determining that the user equipment also communicates with a second node using a second radio access technology; and components for generating a message for transmission to the user equipment, the message including conditional switching information, the conditional switching information including configuration information for communicating with the second node, and a core network indication indicating whether the first node and the second node provide access to one of the following: the same core network, different core networks that are compatible with each other, or different core networks that are incompatible with each other.

[0144] The device may also include components for performing the optional features listed with respect to the methods described above.

[0145] According to various, but not necessarily all, example embodiments of this disclosure, an apparatus is provided comprising: a circuit system configured to provide radio coverage to a user equipment according to a first radio access technology, the apparatus comprising: a circuit system configured to provide the radio coverage to the user equipment within a radio cell; a circuit system configured to determine that the user equipment also communicates with a second node using a second radio access technology; and a circuit system configured to generate a message for transmission to the user equipment, the message including conditional switching information, the conditional switching information including configuration information for communicating with the second node, and a core network indication indicating whether the first node and the second node provide access to one of the following: the same core network, different core networks that are compatible with each other, or different core networks that are incompatible with each other.

[0146] The apparatus may also include a circuit system configured to perform the optional features listed with respect to the above methods.

[0147] According to various, but not necessarily all, example embodiments of this disclosure, a computer program including instructions is provided that, when executed by a device, causes the device to perform at least the following:

[0148] Provide radio coverage to user equipment within a radio cell; determine that the user equipment also communicates with a second node using a second radio access technology; and generate a message for transmission to the user equipment, the message including conditional switching information, the conditional switching information including: configuration information for communicating with the second node, and a core network indication indicating whether the first node and the second node provide access to one of the following: the same core network, different core networks that are compatible with each other, or different core networks that are incompatible with each other.

[0149] According to various, but not necessarily all, example embodiments of this disclosure, a computer-readable medium is provided that includes instructions which, when executed by an apparatus, cause the apparatus to perform at least the following: providing radio coverage to a user equipment within a radio cell; determining that the user equipment also communicates with a second node using a second radio access technology; and generating a message for transmission to the user equipment, the message including conditional switching information, the conditional switching information including: configuration information for communicating with the second node, and a core network indication indicating whether the first node and the second node provide access to one of the following: the same core network, different core networks that are compatible with each other, or different core networks that are incompatible with each other.

[0150] According to various, but not necessarily all, example embodiments of this disclosure, a non-transient computer-readable medium is provided, the non-transient computer-readable medium including program instructions stored thereon for at least performing: causing a device to provide radio coverage to a user equipment within a radio cell; determining that the user equipment is also communicating with a second node using a second radio access technology; and generating a message for transmission to the user equipment, the message including conditional switching information, the conditional switching information including: configuration information for communicating with the second node, and a core network indication indicating whether the first node and the second node provide access to one of the following: the same core network, different core networks that are compatible with each other, or different core networks that are incompatible with each other.

[0151] The instructions detailed above can be used to execute the optional features listed with respect to the methods described above.

[0152] According to various, but not necessarily all, example embodiments of this disclosure, an apparatus is provided for providing radio coverage to a user equipment according to a second radio access technology, the apparatus comprising: at least one processor; and at least one memory storing instructions, which, when executed by the at least one processor, cause the apparatus to at least: provide the radio coverage to the user equipment within a radio cell, the user equipment communicating with a first node using a first radio access technology; receive from the first node a conditional handover request message including configuration information for the user equipment; determine that a conditional handover from the first radio access technology is currently permitted; and, if the conditional handover is permitted, derive updated configuration information from the configuration information for communication between the user equipment and the second node; and send the updated configuration information to the first node.

[0153] Conditional handover is permitted if the base station supports conditional handover and currently has sufficient resources to provide the handover.

[0154] In some embodiments, the device operates as an auxiliary node, and the first node operates as an anchor node.

[0155] In some embodiments, the configuration information includes information related to generating a security key for communicating with the user equipment.

[0156] When the core network is identical or compatible, the security key information may include information that allows security keys to be derived from it. For example, it may include an indication of the root key, and / or an indication of key reuse, and a method for deriving an update key from the root key, or it may include SIM information for multi-SIM embodiments that also allows for the derivation of security keys.

[0157] In some embodiments, the updated configuration information includes information related to generating a security key for communicating with the user equipment.

[0158] The device can provide information about how the user equipment can derive the security key, and this can be based on the security key information it has already received from the second node.

[0159] In some embodiments, the updated configuration information includes an indication that timing and synchronization information should be retained.

[0160] In other embodiments, the device is configured to generate a response to the condition switching request message, the response including timing and synchronization information; and to send the response to the first node.

[0161] In some embodiments, the condition switching request message includes an inter-RAT condition switching request message.

[0162] In some embodiments, the apparatus is also configured to respond to: receiving an inter-RAT conditional handover confirmation message from the user equipment, the inter-RAT conditional handover confirmation message including confirmation that the user equipment is no longer connected to the first node; and deriving and applying an updated security key based on configuration information received in the conditional handover request message.

[0163] In some embodiments, the apparatus is further configured to: respond to receiving an inter-RAT conditional handover confirmation message from a user equipment, the inter-RAT conditional handover confirmation message including confirmation that the user equipment is no longer connected to the first node; and switch to act as an anchor node.

[0164] In some embodiments, the apparatus is also configured to respond to: receiving an inter-RAT condition handover confirmation message from a user equipment, the inter-RAT condition handover confirmation message including an indication of the at least one radio condition that triggered the connection change; and forwarding the indication of the at least one radio condition that triggered the connection change to the first node.

[0165] In some embodiments, the device includes a 5G base station.

[0166] According to various, but not necessarily all, example embodiments of this disclosure, a method is provided for providing radio coverage to a user equipment according to a second radio access technology, the method comprising: providing the radio coverage to the user equipment within a radio cell, the user equipment communicating with a first node using a first radio access technology; receiving from the first node the conditional handover request message including configuration information for the user equipment; determining that conditional handover from the first radio access technology is currently permitted; and, if conditional handover is currently permitted, deriving updated configuration information from the configuration information for communication between the user equipment and the second node; and sending the updated configuration information to the first node.

[0167] In some embodiments, the updated configuration information includes an indication that timing and synchronization information should be retained.

[0168] In other embodiments, the method includes generating a response to the condition switching request message, the response including an indication of at least one of the following: an indication that a timing advance needs to be obtained, or an indication of a value to be applied to the timing advance.

[0169] In some embodiments, the method includes: receiving an inter-RAT conditional handover confirmation message from a user equipment, the inter-RAT conditional handover confirmation message including confirmation that the user equipment is no longer connected to the first node; and deriving and applying an updated security key based on configuration information received in the conditional handover request message.

[0170] In some embodiments, the method includes: receiving an inter-RAT conditional handover confirmation message from a user equipment, the inter-RAT conditional handover confirmation message including confirmation that the user equipment is no longer connected to the first node; and switching to act as an anchor node.

[0171] In some embodiments, the method includes: receiving an inter-RAT condition handover confirmation message from a user equipment, the inter-RAT condition handover confirmation message including an indication of at least one radio condition that triggered the connection change; and forwarding the indication of the at least one radio condition that triggered the connection change to the first node.

[0172] According to various, but not necessarily all, example embodiments of this disclosure, an apparatus is provided for providing radio coverage to a user equipment according to a second radio access technology, the apparatus comprising: components for providing the radio coverage to the user equipment within a radio cell, the user equipment communicating with a first node using a first radio access technology; components for receiving from the first node a conditional handover request message including configuration information for the user equipment; components for determining that conditional handover from the first radio access technology is currently permitted; components for deriving updated configuration information from the configuration information for communication between the user equipment and the second node; and components for sending the updated configuration information to the first node.

[0173] The apparatus may also include components for performing the optional features listed with respect to the methods described above.

[0174] According to various, but not necessarily all, example embodiments of this disclosure, an apparatus is provided comprising: a circuit system configured to provide radio coverage to a user equipment according to a second radio access technology, the apparatus comprising: a circuit system configured to provide the radio coverage to the user equipment within a radio cell, the user equipment communicating with a first node using a first radio access technology; a circuit system configured to receive from the first node a conditional handover request message including configuration information for the user equipment; a circuit system configured to determine that a conditional handover from the first radio access technology is currently permitted; a circuit system configured to derive updated configuration information from the configuration information for communication between the user equipment and the second node; and a circuit system configured to send the updated configuration information to the first node.

[0175] The device may include an additional circuit system configured to perform the optional features listed with respect to the above methods.

[0176] According to various, but not necessarily all, example embodiments of this disclosure, a computer program including instructions is provided that, when executed by a device, causes the device to perform at least the following:

[0177] Within a radio cell, radio coverage is provided to a user equipment (UE) according to a second radio access technology, the UE communicating with a first node using a first radio access technology; a conditional handover request message including configuration information for the UE is received from the first node; a conditional handover from the first radio access technology is determined to be currently permitted; and if the conditional handover is currently permitted, updated configuration information for communication between the UE and the second node is derived from the configuration information; and the updated configuration information is sent to the first node.

[0178] According to various, but not necessarily all, example embodiments of this disclosure, a computer-readable medium including instructions that, when executed by an apparatus, cause the apparatus to perform at least the following: providing radio coverage to a user equipment (UE) within a radio cell according to a second radio access technology, the UE communicating with a first node using a first radio access technology; receiving from the first node a conditional handover request message including configuration information for the UE; determining that a conditional handover from the first radio access technology is currently permitted; and, if the conditional handover is currently permitted, deriving updated configuration information from the configuration information for communication between the UE and the second node; and sending the updated configuration information to the first node.

[0179] According to various, but not necessarily all, example embodiments of this disclosure, a non-transient computer-readable medium is provided, comprising program instructions stored thereon for performing at least the following: causing a device to provide radio coverage to a user equipment within a radio cell according to a second radio access technology, the user equipment communicating with a first node using a first radio access technology; receiving from the first node a conditional handover request message including configuration information for the user equipment; determining that a conditional handover from the first radio access technology is currently permitted; and, if a conditional handover is currently permitted, deriving updated configuration information from the configuration information for communication between the user equipment and the second node; and sending the updated configuration information to the first node.

[0180] The instructions detailed above can be used to execute the optional features listed with respect to the methods described above.

[0181] According to various, but not necessarily all, example embodiments of this disclosure, an apparatus is provided, the apparatus including at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus to at least: operate in a mode causing the apparatus to communicate with a first node and a second node using different Radio Access Technologies (RATs); respond to receiving conditional handover information (5) from the first node, the conditional handover information including configuration information for the second node and a core network indication regarding whether the first node and the second node provide access to one of the following: the same core network, or different core networks that are compatible with each other, or different core networks that are incompatible with each other; determine whether at least one handover condition is satisfied; and, if at least one handover condition is satisfied, initiate a handover process by: generating a handover confirmation report, the handover confirmation report including an indication of the at least one handover condition determined to be satisfied;

[0182] Send the report to the second node; and perform the switch such that the device is no longer connected to the first node and the device is connected to the second node.

[0183] The device determines whether the handover conditions are met and triggers a conditional handover between cells provided by nodes using different RAT operations. The device generates a handover confirmation report that includes information about the conditions that triggered the handover.

[0184] In some embodiments, the device is configured to operate in a mode comprising a dual connectivity mode, wherein the first node acts as an anchor node for the device and the second node acts as an auxiliary node; and after the switching, the second node acts as the anchor node for the device.

[0185] In other embodiments, the device is configured to operate with a plurality of SIMs, a first SIM for communicating with a first radio access technology of the first node, and a second SIM for communicating with a second radio access technology of the second node.

[0186] In some embodiments where the device is configured to operate with multiple SIM cards, the device is also configured to: generate a message indicating that the device is connected to both the first node and the second node; and send the message to the first node.

[0187] In some embodiments, the first node operates in a higher frequency band than the second node, and thus can provide a cell with a smaller radio coverage area than the cell of the second node, and the device is more likely to lose connection with the first node before losing connection with the second node.

[0188] The first node may include a 6G node, and the second node may include a 5G node.

[0189] In some embodiments, the apparatus is configured to: in response to a core network indication received indicating that the core networks used for the first node and the second node are the same or compatible core networks, apply a user plane data routing procedure based on configuration information received within the conditional switching information from the first node.

[0190] In some embodiments, the apparatus is configured to: determine from the core network indication whether the core network is the same or compatible core network, and if so, derive a security key for the second node from the condition switching information; and if not, generate a new security key.

[0191] In some embodiments, in response to received configuration information indicating that the synchronization information and timing advance are to be reused, the apparatus is configured to retain the synchronization and timing advance configuration when performing the switch to the second node.

[0192] In some embodiments, determining whether the switching condition is met includes determining whether at least one radio condition for communicating with the first node does not meet at least one predetermined threshold.

[0193] In some embodiments, the at least one switching condition is satisfied when:

[0194] The number of uplink retransmissions is higher than the configured maximum retransmission value.

[0195] In some embodiments, the at least one switching condition is satisfied when:

[0196] The number of uplink retransmissions is less than the configured maximum retransmission value; and at least one uplink pseudotransmission is executed and fails.

[0197] In some embodiments, the at least one switching condition is satisfied when:

[0198] The measured signal strength of the signal from the first node is lower than the configured threshold.

[0199] In some embodiments, the at least one switching condition is satisfied when:

[0200] The packet error rate in Layer 1 or Layer 2 exceeds the configured threshold within a predetermined time period during which the signaling notification is sent to the first node.

[0201] In some embodiments, the apparatus is configured to: perform a determination that at least two of the switching conditions are satisfied before initiating the switching process.

[0202] In some embodiments, determining whether the at least one handover condition is met includes: comparing the packet error rate in Layer 1 or Layer 2 within a predetermined time period during which signaling is sent to the first node with a configured threshold, and if the packet error rate is higher than the predetermined threshold: comparing the number of uplink retransmissions with a configured threshold; and if the number of uplink retransmissions is higher than the configured threshold, determining that the handover condition is met.

[0203] In some cases, in addition to determining that the packet error rate is higher than the predetermined amount, uplink retransmissions can also be checked, and the switching condition is met only if both of the thresholds are met.

[0204] In some embodiments, determining whether the at least one handover condition is met includes: comparing the packet error rate in Layer 1 or Layer 2 signals within a predetermined time period for which signaling notification is sent to the first node with a configured threshold; if the packet error rate is higher than the predetermined threshold: comparing the number of uplink retransmissions with a configured threshold; and if the number of retransmissions is higher than the configured threshold, determining that the handover condition is met; and wherein at least one additional uplink pseudo-transmission is not performed; and if the at least one uplink pseudo-transmission fails, determining that the at least one handover condition is to be met.

[0205] In some embodiments, in addition to determining that the packet error rate is higher than a predetermined amount and the uplink retransmission is higher than a certain amount, if the uplink retransmission is not higher than that amount, they can be checked by sending uplink dummy data, and if the check fails, the handover condition can be considered met. This may be necessary when the device is not currently sending uplink signals regularly, and therefore, there may be no transmission failures despite poor radio conditions.

[0206] In some embodiments, in response to determining that the device has disconnected from the first node and then reconnected to the first node more than a predetermined number of times within a predetermined time period, the device is caused to update at least one of the switching conditions.

[0207] In some embodiments, the device may check whether it has already pinged between cells, which is a handover from one cell and then returns again within a short period of time. If it has already pinged between cells, this is an indication that the device may be handing over the cell too early, and the device may adjust the threshold conditions to make them harder to meet and thus make the handover less frequent in order to reduce the number of these pings.

[0208] In some embodiments, the apparatus is configured to: provide an updated indication of the at least one switching condition within the switching confirmation report.

[0209] In some embodiments, the device is further configured to: determine the mobility of the device, and, in the case of low mobility, delay initiating the handover process.

[0210] For example, when the device is stationary, its mobility is considered low.

[0211] In some embodiments, the step of performing the handover includes applying a user plane data routing procedure based on the configuration information received within the conditional handover information from the first node.

[0212] In some embodiments, the apparatus includes user equipment.

[0213] According to various, but not necessarily all, example embodiments of this disclosure, a method is provided to be performed on an apparatus, the method comprising: operating in a mode that enables the apparatus to communicate with a first node and a second node using different Radio Access Technologies (RATs); receiving conditional handover information from the first node, the conditional handover information including configuration information for the second node and a core network indication regarding whether the first node and the second node provide access to one of the following: the same core network, or different core networks that are compatible with each other, or different core networks that are incompatible with each other; determining whether at least one handover condition is satisfied; and when at least one handover condition is satisfied, initiating a handover process by: generating a handover confirmation report, the handover confirmation report including: an indication of the at least one handover condition determined to be satisfied; sending the report to the second node; and performing the handover such that the apparatus is no longer connected to the first node and the apparatus is connected to the second node.

[0214] In some embodiments where the device operates with multiple SIM cards, the method includes: generating a message indicating that the device is connected to both a first node and a second node; and sending the message to the first node.

[0215] In some embodiments, the method includes: applying a user plane data routing procedure based on configuration information received within the conditional switching information from the first node, provided that the core network indication indicates that the core networks for the first node and the second node are the same or compatible core networks.

[0216] In some embodiments, the method includes determining from the core network indication whether the core network is the same or compatible core network, and if the core network is the same or compatible core network, deriving a security key for the second node from the condition switching information; and if the core network is not the same or compatible core network, generating a new security key.

[0217] In some embodiments, in response to received configuration information indicating that the synchronization information and timing advance are to be reused, the method includes: retaining the synchronization and timing advance configuration when performing the switch to the second node.

[0218] In some embodiments, determining whether the switching condition is met includes determining whether at least one radio condition for communicating with the first node does not meet at least one predetermined threshold.

[0219] In some embodiments, the method includes: determining that at least two of the switching conditions are satisfied before initiating the switching process.

[0220] In some embodiments, determining whether the at least one handover condition is met includes: comparing the packet error rate of Layer 1 or Layer 2 within a predetermined time period during which signaling notification is sent to the first node with a configured threshold; and if the packet error rate is higher than the predetermined threshold: comparing the number of uplink retransmissions with a configured threshold; and if the number of uplink retransmissions is higher than the configured threshold, determining that the handover condition is met.

[0221] In some embodiments, determining whether the at least one handover condition is met includes: comparing the packet error rate of Layer 1 or Layer 2 within a predetermined time period during which signaling notification is sent to the first node with a configured threshold; if the packet error rate is higher than the predetermined threshold: comparing the number of uplink retransmissions with a configured threshold; and if the number of retransmissions is higher than the configured threshold, determining that the handover condition is met; and wherein at least one additional uplink pseudo-transmission is not performed; and if the at least one uplink pseudo-transmission fails, determining that the at least one handover condition is to be met.

[0222] In some embodiments, the method includes: updating at least one of the switching conditions in response to determining that the device has disconnected from the first node and then reconnected to the first node more than a predetermined number of times within a predetermined time period.

[0223] In some embodiments, the method includes providing an updated indication of the at least one switching condition within the switching confirmation report.

[0224] In some embodiments, the method includes determining the mobility of the device and delaying the initiation of the handover process if the mobility is low.

[0225] In some embodiments, the step of performing the handover includes applying a user plane data routing procedure based on the configuration information received within the conditional handover information from the first node.

[0226] According to various, but not necessarily all, example embodiments of this disclosure, an apparatus is provided comprising: components for operating in a mode that enables the apparatus to communicate with a first node and a second node using different Radio Access Technologies (RATs); components for receiving conditional handover information from the first node, the conditional handover information including configuration information for the second node and a core network indication regarding whether the first node and the second node provide access to one of the following: the same core network, or different core networks that are compatible with each other, or different core networks that are incompatible with each other; components for determining whether at least one handover condition is satisfied; and, if at least one handover condition is satisfied, initiating a handover process by triggering the following operations: components for generating a handover confirmation report, the handover confirmation report including: an indication of the at least one handover condition determined to be satisfied; components for sending the report to the second node; and components for performing the handover such that the apparatus is no longer connected to the first node and the apparatus is connected to the second node.

[0227] The apparatus may also include components for performing the optional features listed with respect to the methods described above.

[0228] According to various, but not necessarily all, example embodiments of this disclosure, an apparatus is provided comprising: a circuit system configured to operate in a mode that enables the apparatus to communicate with a first node and a second node using different Radio Access Technologies (RATs); a circuit system configured to receive conditional handover information from the first node, the conditional handover information including configuration information for the second node and a core network indication regarding whether the first node and the second node provide access to one of the following: the same core network, or different core networks that are compatible with each other, or different core networks that are incompatible with each other; a circuit system configured to determine whether at least one handover condition is satisfied, and, if at least one handover condition is satisfied, to initiate a handover process by triggering the following operations: a circuit system configured to generate a handover confirmation report, the handover confirmation report including: an indication of the at least one handover condition that is determined to be satisfied; a circuit system configured to send the report to the second node; and a circuit system configured to perform the handover such that the apparatus is no longer connected to the first node and the apparatus is connected to the second node.

[0229] The device may include an additional circuit system configured to perform the optional features listed with respect to the above methods.

[0230] According to various, but not necessarily all, example embodiments of this disclosure, a computer program including instructions is provided that, when executed by a device, causes the device to perform at least the following:

[0231] Operating in a mode that enables the device to communicate with a first node and a second node using different Radio Access Technologies (RATs), the device receives conditional handover information from the first node, the conditional handover information including configuration information for the second node and a core network indication regarding whether the first node and the second node provide access to one of the following: the same core network, or different core networks that are compatible with each other, or different core networks that are incompatible with each other; determines whether at least one handover condition is met; and, if at least one handover condition is met, initiates a handover process by: generating a handover confirmation report, the handover confirmation report including: an indication of the at least one handover condition determined to be met; sending the report to the second node; and performing the handover such that the device is no longer connected to the first node and the device is connected to the second node.

[0232] According to various, but not necessarily all, example embodiments of this disclosure, a computer-readable medium including instructions that, when executed by a device, cause the device to perform at least the following: operating in a mode that enables the device to communicate with a first node and a second node using different Radio Access Technologies (RATs); receiving conditional handover information from the first node, the conditional handover information including configuration information for the second node and a core network indication regarding whether the first node and the second node provide access to one of the following: the same core network, or different core networks that are compatible with each other, or different core networks that are incompatible with each other; determining whether at least one handover condition is satisfied; and, if at least one handover condition is satisfied, initiating a handover process by: generating a handover confirmation report, the handover confirmation report including: an indication of the at least one handover condition determined to be satisfied; sending the report to the second node; and performing the handover such that the device is no longer connected to the first node and the device is connected to the second node.

[0233] According to various, but not necessarily all, example embodiments of this disclosure, a non-transient computer-readable medium is provided, the non-transient computer-readable medium including program instructions stored thereon for performing at least the following: causing a device to operate in a mode that enables the device to communicate with a first node and a second node using different Radio Access Technologies (RATs); receiving conditional handover information from the first node, the conditional handover information including configuration information for the second node and a core network indication regarding whether the first node and the second node provide access to one of the following: the same core network, or different core networks that are compatible with each other, or different core networks that are incompatible with each other; determining whether at least one handover condition is satisfied; and, if at least one handover condition is satisfied, initiating a handover process by: generating a handover confirmation report, the handover confirmation report including: an indication of the at least one handover condition determined to be satisfied; sending the report to the second node; and performing the handover such that the device is no longer connected to the first node and the device is connected to the second node.

[0234] The instructions detailed above can be used to execute the optional features listed with respect to the methods described above.

[0235] Those skilled in the art will readily recognize that the steps of the various methods described above can be performed by a programmed computer. Some embodiments are also intended to cover program storage devices, such as digital data storage media, that are machine- or computer-readable and encode machine-executable or computer-executable programs of instructions that perform some or all of the steps of the methods described above. Program storage devices can be, for example, digital memories, magnetic storage media such as disks and tapes, hard disk drives, or optically readable digital data storage media. These embodiments are also intended to cover computers programmed to perform the steps of the methods described above. The term "non-transient" as used herein refers to a limitation on the medium itself (i.e., tangible, not tactile), rather than a limitation on the persistence of data storage (e.g., RAM versus ROM).

[0236] As used in this application, the term "circuit system" may refer to one or more or all of the following:

[0237] (a) Implementation of hardware circuits only (such as implementation only in analog and / or digital circuit systems) and

[0238] (b) A combination of hardware circuitry and software, such as (if applicable):

[0239] (i) A combination of (multiple) analog and / or digital hardware circuits and software / firmware, and

[0240] (ii) Any part of a hardware processor(s) having software (including multiple digital signal processors(s)), software, and memory(s), which work together to enable a device such as a mobile phone or server to perform various functions.

[0241] as well as

[0242] (c) Multiple hardware circuits and / or multiple processors (such as multiple microprocessors or a portion thereof) are required for operation of software (e.g., firmware), but the software may not be present when operation is not required.

[0243] The definition of "circuit system" applies to all uses of the term in this application (including in any claim). As another example, as used in this application, the term "circuit system" also covers implementations of hardware circuitry or processors (or processors in general) and a portion thereof, along with their accompanying software and / or firmware. The term "circuit system" also covers (e.g., and if applicable to a particular claim element) baseband integrated circuits or processor integrated circuits for mobile devices, or similar integrated circuits in servers, cellular network devices, or other computing or network devices.

[0244] As used herein, “at least one of the following: ” and “at least one of ” and similar wording (where a list of two or more elements is connected by “and” or “or”) means at least any one element, or at least any two or more elements, or at least all elements.

[0245] The order of the steps listed above may not be critical or fixed, and the exact order of the steps may be changed appropriately.

[0246] Although exemplary embodiments of the invention have been described with reference to various examples in the preceding paragraphs, it should be understood that modifications may be made to the given examples without departing from the scope of the claimed invention.

[0247] The features described above can be used in combinations other than those explicitly described.

[0248] Although the functionality has been described with reference to certain features, these functions can be performed by other features regardless of whether they are described or not.

[0249] Although features have been described with reference to certain embodiments, these features may exist in other embodiments, whether or not they are described.

[0250] Although efforts have been made in the foregoing description to draw attention to those features of the invention that are considered particularly important, it should be understood that the applicant claims protection for any patentable features or combinations thereof mentioned above and / or shown in the drawings, regardless of whether they have been specifically emphasized.

Claims

1. A device for communication, comprising: At least one processor; as well as At least one memory stores instructions that, when executed by the at least one processor, cause the device to at least: The device operates in a mode that enables it to communicate with a first node and a second node using different Radio Access Technologies (RATs). The system responds to receiving conditional switching information from the first node, the conditional switching information including: configuration information for the second node, and a core network indication regarding whether the first node and the second node provide access to one of the following: the same core network, or different core networks that are compatible with each other, or different core networks that are incompatible with each other. Determine whether at least one switching condition is met; and when at least one switching condition is met, initiate the switching procedure via the following: Generate a handover confirmation report, the handover confirmation report including: an indication of the at least one handover condition determined to be met; Send the report to the second node; and The switching is performed such that the device is no longer connected to the first node and is connected to the second node.

2. The apparatus of claim 1, wherein the apparatus is configured to operate in a mode comprising a dual connectivity mode, the first node acting as an anchor node for the apparatus, and the second node acting as an auxiliary node; and After the switch, the second node acts as the anchor node for the device.

3. The apparatus of claim 1, wherein the apparatus is configured to operate with a plurality of SIMs, a first SIM for communicating with a first radio access technology of the first node, and a second SIM for communicating with a second radio access technology of the second node.

4. The apparatus according to any of the preceding claims, wherein the apparatus is configured such that: In response to a received core network indication that the core networks used for the first node and the second node are the same or compatible core networks, a user plane data routing procedure is applied based on the configuration information received from the first node within the condition switching information.

5. The apparatus according to any of the preceding claims, wherein the apparatus is configured to: determine from the core network indication whether the core network is the same or compatible core network, and if so, derive a security key for the second node from the condition switching information; and if not, generate a new security key.

6. The apparatus according to any of the preceding claims, wherein in response to the received configuration information indicating that the synchronization information and timing advance will be reused, the apparatus is configured to: retain the synchronization and timing advance configuration when performing the switch to the second node.

7. The apparatus according to any preceding claim, wherein determining whether the at least one switching condition is satisfied comprises: The at least one attribute of the uplink or downlink radio conditions used for communicating with the first node will be compared with at least one predetermined threshold.

8. The apparatus according to any of the preceding claims, wherein the at least one switching condition is satisfied when: The number of uplink retransmissions is higher than the configured maximum retransmission value.

9. The apparatus according to any one of claims 1 to 7, wherein the at least one switching condition is satisfied when: The number of uplink retransmissions is lower than the configured maximum retransmission value; and At least one uplink pseudo-transmission was executed and failed.

10. The apparatus according to any of the preceding claims, wherein the at least one switching condition is satisfied when: The measured signal strength of the signal from the first node is lower than the configured threshold.

11. The apparatus according to any of the preceding claims, wherein the at least one switching condition is satisfied when: The packet error rate in Layer 1 or Layer 2 exceeds the configured threshold within a predetermined time period during which the signaling notification is sent to the first node.

12. The apparatus according to any one of claims 8 to 11, wherein the apparatus is configured to: before initiating the switching process, perform a determination that at least two of the switching conditions are satisfied.

13. The apparatus according to any of the preceding claims, wherein the apparatus is configured to: update at least one of the at least one switching condition in response to determining that the apparatus has been disconnected from the first node and then reconnecting to the first node more than a predetermined number of times within a predetermined time period.

14. The apparatus of claim 13, wherein the apparatus is configured to: provide an updated indication of the at least one switching condition within the switching confirmation report.

15. The apparatus according to any one of claims 7 to 14, further comprising: determining the mobility of the apparatus, and, in the case of low mobility, delaying the initiation of the switching process.

16. A method for communication executed on a device, the method comprising: The device operates in a mode that enables it to communicate with a first node and a second node using different Radio Access Technologies (RATs). Receive condition switching information from the first node, the condition switching information including: configuration information for the second node, and core network indication regarding whether the first node and the second node provide access to one of the following: the same core network, or different core networks that are compatible with each other, or different core networks that are incompatible with each other; Determine whether at least one switching condition is met; and when at least one switching condition is met, initiate the switching procedure via the following: Generate a handover confirmation report, the handover confirmation report including: an indication of the at least one handover condition determined to be met; Send the report to the second node; and The switching is performed such that the device is no longer connected to the first node and is connected to the second node.

17. An apparatus for communication, comprising: Components for operation in a mode in which the device communicates with a first node and a second node using different radio access technologies (RATs); A component for receiving conditional switching information from the first node, the conditional switching information including: configuration information for the second node, and a core network indication regarding whether the first node and the second node provide access to one of the following: the same core network, or different core networks that are compatible with each other, or different core networks that are incompatible with each other; A component used to determine whether at least one switching condition is met; and when at least one switching condition is met, to initiate a switching process by triggering the following operations: A component for generating a handover confirmation report, the handover confirmation report including: an indication of the at least one handover condition determined to be met; Components for sending the report to the second node; and A component for performing the switching so that the device is no longer connected to the first node and is connected to the second node.

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