Not so early data forwarding

Abstract

An apparatus includes at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus at least to: determine whether to transmit one of: an indication to initiate data forwarding, or an indication to stop data forwarding; and transmit, to a network entity, one of: the indication to initiate data forwarding, or the indication to stop data forwarding.

Description

Not So Early Data ForwardingTECHNICAL FIELD

[0001] The examples and non-limiting example embodiments relate generally to communications and, more particularly, to not so early data forwarding.BACKGROUND

[0002] It is known for a communication device to gain access to a communication network via an access network node.SUMMARY

[0003] In accordance with an aspect, an apparatus includes at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus at least to: determine whether to transmit one of: an indication to initiate data forwarding, or an indication to stop data forwarding; and transmit, to a network entity, one of: the indication to initiate data forwarding, or the indication to stop data forwarding.

[0004] In accordance with an aspect, an apparatus includes at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus at least to: receive, from a network entity, one of: an indication to initiate data forwarding, or an indication to stop data forwarding; and perform one of: transmit a bearer context modification request in response to receiving from the network entity the indication to initiate data forwarding, or stop data forwarding in response to receiving from the network entity the indication to stop data forwarding.

[0005] In accordance with an aspect, an apparatus includes at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus at least to: receive, from a network entity, a handover request; and receive, from the network entity, an indication of a stopping of data forwarding; wherein the indication of the stopping of data forwarding is based on transmission configuration indicator state deactivation, a timing advance validity expiration, a cell switch command, target cell measurements from a layer 1 report, or a triggering of a timing advance acquisition.

[0006] In accordance with an aspect, an apparatus includes at least one processor; and atleast one memory storing instructions that, when executed by the at least one processor, cause the apparatus at least to: transmit, to a network entity, a measurement report; wherein the measurement report is configured to be used with the network entity to determine whether to initiate data forwarding or stop data forwarding; and receive, from the network entity, an indication related to the determination of whether to initiate data forwarding or stop data forwarding.

[0007] In accordance with an aspect, an apparatus includes at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus at least to: receive, from a network entity, a bearer context modification request comprising an indication to initiate data forwarding; wherein the bearer context modification request comprising the indication to initiate data forwarding is based on one of: transmission configuration indicator state activation, early timing advance acquisition, a physical downlink control channel ordered random access channel, or a layer 3 measurement report that indicates that a reference signal received power or reference signal received quality value of a serving cell or candidate cell is above or below a threshold; and initiate data forwarding, based on the bearer context modification request comprising the indication to initiate data forwarding received from the network entity.BRIEF DESCRIPTION OF THE DRAWINGS

[0008] The foregoing aspects and other features are explained in the following description, taken in connection with the accompanying drawings.

[0009] FIG. 1 is a block diagram of one possible and non-limiting system in which the example embodiments may be practiced.

[0010] FIG. 2 shows Ll / 2 triggered mobility without CU-UP change.

[0011] FIG. 3 shows Ll / 2 triggered mobility with CU-UP change.

[0012] FIG. 4 shows Solution 1 using TCI state activation as a trigger.

[0013] FIG. 5 shows Solution 1 using a PDCCH order transmission as a trigger.

[0014] FIG. 6 shows an example using an L3 measurement report.

[0015] FIG. 7 shows Solution 2 for data forwarding stop.

[0016] FIG. 8 is an example apparatus configured to implement the examples described herein.

[0017] FIG. 9 shows a representation of an example of non-volatile memory media used to store instructions that implement the examples described herein.

[0018] FIG. 10 is an example method, based on the examples described herein.

[0019] FIG. 11 is an example method, based on the examples described herein.

[0020] FIG. 12 is an example method, based on the examples described herein.

[0021] FIG. 13 is an example method, based on the examples described herein.

[0022] FIG. 14 is an example method, based on the examples described herein.DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

[0023] Turning to FIG. 1, this figure shows a block diagram of one possible and nonlimiting example in which the examples may be practiced. A user equipment (UE) 110, radio access network (RAN) node 170, and network element(s) 190 are illustrated. In the example of FIG. 1, the user equipment (UE) 110 is in wireless communication with a wireless network 100. A UE is a wireless device that can access the wireless network 100. The UE 110 includes one or more processors 120, one or more memories 125, and one or more transceivers 130 interconnected through one or more buses 127. Each of the one or more transceivers 130 includes a receiver, Rx, 132 and a transmitter, Tx, 133. The one or more buses 127 may be address, data, or control buses, and may include any interconnection mechanism, such as a series of lines on a motherboard or integrated circuit, fiber optics or other optical communication equipment, and the like. The one or more transceivers 130 are connected to one or more antennas 128. The one or more memories 125 include computer program code 123. The UE 110 includes a module 140, comprising one of or both parts 140-1 and / or 140- 2, which may be implemented in a number of ways. The module 140 may be implemented in hardware as module 140-1, such as being implemented as part of the one or more processors 120. The module 140-1 may be implemented also as an integrated circuit or through other hardware such as a programmable gate array. In another example, the module 140 may be implemented as module 140-2, which is implemented as computer program code 123 and is executed by the one or more processors 120. For instance, the one or more memories 125and the computer program code 123 may be configured to, with the one or more processors 120, cause the user equipment 110 to perform one or more of the operations as described herein. The UE 110 communicates with RAN node 170 via a wireless link 111.

[0024] The RAN node 170 in this example is a base station that provides access for wireless devices such as the UE 110 to the wireless network 100. The RAN node 170 may be, for example, a base station for 5G, also called New Radio (NR). In 5G, the RAN node 170 may be a NG-RAN node, which is defined as either a gNB or an ng-eNB. A gNB is a node providing NR user plane and control plane protocol terminations towards the UE, and connected via the NG interface (such as connection 131) to a 5GC (such as, for example, the network element(s) 190). The ng-eNB is a node providing E-UTRA user plane and control plane protocol terminations towards the UE, and connected via the NG interface (such as connection 131) to the 5GC. The NG-RAN node may include multiple gNBs, which may also include a central unit (CU) (gNB-CU) 196 and distributed unit(s) (DUs) (gNB-DUs), of which DU 195 is shown. Note that the DU 195 may include or be coupled to and control a radio unit (RU). The gNB-CU 196 is a logical node hosting radio resource control (RRC), SDAP and PDCP protocols of the gNB or RRC and PDCP protocols of the en-gNB that control the operation of one or more gNB-DUs. The gNB-CU 196 terminates the Fl interface connected with the gNB-DU 195. The Fl interface is illustrated as reference 198, although reference 198 also illustrates a link between remote elements of the RAN node 170 and centralized elements of the RAN node 170, such as between the gNB-CU 196 and the gNB- DU 195. The gNB-DU 195 is a logical node hosting RLC, MAC and PHY layers of the gNB or en-gNB, and its operation is partly controlled by gNB-CU 196. One gNB-CU 196 supports one or multiple cells. One cell may be supported with one gNB-DU 195, or one cell may be supported / shared with multiple DUs under RAN sharing. The gNB-DU 195 terminates the Fl interface 198 connected with the gNB-CU 196. Note that the DU 195 is considered to include the transceiver 160, e.g., as part of a RU, but some examples of this may have the transceiver 160 as part of a separate RU, e.g., under control of and connected to the DU 195. The RAN node 170 may also be an eNB (evolved NodeB) base station, for LTE (long term evolution), or any other suitable base station or node.

[0025] The RAN node 170 includes one or more processors 152, one or more memories 155, one or more network interfaces (N / W I / F(s)) 161, and one or more transceivers 160 interconnected through one or more buses 157. Each of the one or more transceivers 160includes a receiver, Rx, 162 and a transmitter, Tx, 163. The one or more transceivers 160 are connected to one or more antennas 158. The one or more memories 155 include computer program code 153. The CU 196 may include the processor(s) 152, one or more memories 155, and network interfaces 161. Note that the DU 195 may also contain its own memory / memories and processor(s), and / or other hardware, but these are not shown.

[0026] The RAN node 170 includes a module 150, comprising one of or both parts 150-1 and / or 150-2, which may be implemented in a number of ways. The module 150 may be implemented in hardware as module 150-1, such as being implemented as part of the one or more processors 152. The module 150-1 may be implemented also as an integrated circuit or through other hardware such as a programmable gate array. In another example, the module 150 may be implemented as module 150-2, which is implemented as computer program code 153 and is executed by the one or more processors 152. For instance, the one or more memories 155 and the computer program code 153 are configured to, with the one or more processors 152, cause the RAN node 170 to perform one or more of the operations as described herein. Note that the functionality of the module 150 may be distributed, such as being distributed between the DU 195 and the CU 196, or be implemented solely in the DU 195.

[0027] The one or more network interfaces 161 communicate over a network such as via the links 176 and 131. Two or more gNBs 170 may communicate using, e.g., link 176. The link 176 may be wired or wireless or both and may implement, for example, an Xn interface for 5G, an X2 interface for LTE, or other suitable interface for other standards.

[0028] The one or more buses 157 may be address, data, or control buses, and may include any interconnection mechanism, such as a series of lines on a motherboard or integrated circuit, fiber optics or other optical communication equipment, wireless channels, and the like. For example, the one or more transceivers 160 may be implemented as a remote radio head (RRH) 195 for LTE or a distributed unit (DU) 195 for gNB implementation for 5G, with the other elements of the RAN node 170 possibly being physically in a different location from the RRH / DU 195, and the one or more buses 157 could be implemented in part as, for example, fiber optic cable or other suitable network connection to connect the other elements (e.g., a central unit (CU), gNB-CU 196) of the RAN node 170 to the RRH / DU 195. Reference 198 also indicates those suitable network link(s).

[0029] A RAN node / gNB can comprise one or more TRPs to which the methods described herein may be applied. FIG. 1 shows that the RAN node 170 comprises TRP 51 and TRP 52, in addition to the TRP represented by transceiver 160. Similar to transceiver 160, TRP 51 and TRP 52 may each include a transmitter and a receiver. The RAN node 170 may host or comprise other TRPs not shown in FIG. 1.

[0030] A relay node in NR is called an integrated access and backhaul node. A mobile termination part of the IAB node facilitates the backhaul (parent link) connection. In other words, the mobile termination part comprises the functionality which carries UE functionalities. The distributed unit part of the IAB node facilitates the so called access link (child link) connections (i.e. for access link UEs, and backhaul for other IAB nodes, in the case of multi-hop IAB). In other words, the distributed unit part is responsible for certain base station functionalities. The IAB scenario may follow the so called split architecture, where the central unit hosts the higher layer protocols to the UE and terminates the control plane and user plane interfaces to the 5G core network.

[0031] It is noted that the description herein indicates that “cells” perform functions, but it should be clear that equipment which forms the cell may perform the functions. The cell makes up part of a base station. That is, there can be multiple cells per base station. For example, there could be three cells for a single carrier frequency and associated bandwidth, each cell covering one-third of a 360 degree area so that the single base station’s coverage area covers an approximate oval or circle. Furthermore, each cell can correspond to a single carrier and a base station may use multiple carriers. So if there are three 120 degree cells per carrier and two carriers, then the base station has a total of 6 cells.

[0032] The wireless network 100 may include a network element or elements 190 that may include core network functionality, and which provides connectivity via a link or links 181 with a further network, such as a telephone network and / or a data communications network (e.g., the Internet). Such core network functionality for 5G may include location management functions (LMF(s)) and / or access and mobility management function(s) (AMF(S)) and / or user plane functions (UPF(s)) and / or session management function(s) (SMF(s)). Such core network functionality for LTE may include MME (mobility management entity) / SGW (serving gateway) functionality. Such core network functionality may include SON (self- organizing / optimizing network) functionality. These are merely example functions that may be supported by the network element(s) 190, and note that both 5G and LTE functions mightbe supported. The RAN node 170 is coupled via a link 131 to the network element 190. The link 131 may be implemented as, e.g., an NG interface for 5G, or an SI interface for LTE, or other suitable interface for other standards. The network element 190 includes one or more processors 175, one or more memories 171, and one or more network interfaces (N / W I / F(s)) 180, interconnected through one or more buses 185. The one or more memories 171 include computer program code 173. Computer program code 173 may include SON and / or MRO functionality 172.

[0033] The wireless network 100 may implement network virtualization, which is the process of combining hardware and software network resources and network functionality into a single, software-based administrative entity, or a virtual network. Network virtualization involves platform virtualization, often combined with resource virtualization. Network virtualization is categorized as either external, combining many networks, or parts of networks, into a virtual unit, or internal, providing network-like functionality to software containers on a single system. Note that the virtualized entities that result from the network virtualization are still implemented, at some level, using hardware such as processors 152 or 175 and memories 155 and 171, and also such virtualized entities create technical effects.

[0034] The computer readable memories 125, 155, and 171 may be of any type suitable to the local technical environment and may be implemented using any suitable data storage technology, such as semiconductor based memory devices, flash memory, magnetic memory devices and systems, optical memory devices and systems, non-transitory memory, transitory memory, fixed memory and removable memory. The computer readable memories 125, 155, and 171 may be means for performing storage functions. The processors 120, 152, and 175 may be of any type suitable to the local technical environment, and may include one or more of general purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs) and processors based on a multi-core processor architecture, as nonlimiting examples. The processors 120, 152, and 175 may be means for performing functions, such as controlling the UE 110, RAN node 170, network element(s) 190, and other functions as described herein.

[0035] In general, the various example embodiments of the user equipment 110 can include, but are not limited to, cellular telephones such as smart phones, tablets, personal digital assistants (PDAs) having wireless communication capabilities, portable computers having wireless communication capabilities, image capture devices such as digital cameras havingwireless communication capabilities, gaming devices having wireless communication capabilities, music storage and playback devices having wireless communication capabilities, internet appliances including those permitting wireless internet access and browsing, tablets with wireless communication capabilities, head mounted displays such as those that implement virtual / augmented / mixed reality, as well as portable units or terminals that incorporate combinations of such functions. The UE 110 can also be a vehicle such as a car, or a UE mounted in a vehicle, a UAV such as e.g. a drone, or a UE mounted in a UAV. The user equipment 110 may be terminal device, such as mobile phone, mobile device, sensor device etc., the terminal device being a device used by the user or not used by the user.

[0036] UE 110, RAN node 170, and / or network element(s) 190, (and associated memories, computer program code and modules) may be configured to implement (e.g. in part) the methods described herein. Thus, computer program code 123, module 140-1, module 140-2, and other elements / features shown in FIG. 1 of UE 110 may implement user equipment related aspects of the examples described herein. Similarly, computer program code 153, module 150-1, module 150-2, and other elements / features shown in FIG. 1 of RAN node 170 may implement gNB / TRP related aspects of the examples described herein. Computer program code 173 and other elements / features shown in FIG. 1 of network element(s) 190 may be configured to implement network element related aspects of the examples described herein.

[0037] Having thus introduced a suitable but non-limiting technical context for the practice of the example embodiments, the example embodiments are now described with greater specificity.

[0038] Ll / 2 Triggered Mobility

[0039] LTM procedure is captured in TS38.300 and TS38.401. The description provided in TS38.401 describe the interactions between CU and DUs. The procedure is shown in FIG. 2 and follows the following steps (1-26), where FIG. 2 shows the signaling exchange between the UE 110, the source gNB-DU 210, the candidate gNB-DU 220, and the gNB-CU 230:

[0040] 1. The UE sends a MeasurementReport message (L3 measurement result) to the source gNB-DU containing measurements of neighboring cells. The source gNB-DU sends an UL RRC MESSAGE TRANSFER message conveying the received MeasurementReport message to the gNB-CU.

[0041] 2. The gNB-CU determines to initiate LTM configuration.

[0042] 3. The gNB-CU sends a UE CONTEXT SETUP REQUEST message to the candidate gNB-DU(s), containing one target candidate cell ID, the LTM configuration ID of the candidate cell, LTM configuration ID mapping list, and the CSI resource configuration. The gNB-CU indicates the source gNB-DU ID, and requests PRACH resources from the candidate gNB-DU. The gNB-CU may request the candidate gNB-DU to provide the lower layer configuration for the purpose of generating the reference configuration.

[0043] 4. If the candidate gNB-DU accepts the request of LTM configuration, it responds with a UE CONTEXT SETUP RESPONSE message including the generated lower layer RRC configurations (e.g., TCI state configuration, RACH configuration, and the CSI report configuration) for the accepted target candidate cell.

[0044] 5. The gNB-CU sends a UE CONTEXT MODIFICATION REQUEST message to the source gNB-DU including the collected CSI report configuration, RACH configuration and the TCI state configuration for the accepted target candidate cell(s) in other gNB-DU(s).

[0045] 6. The source gNB-DU responds with a UE CONTEXT MODIFICATION RESPONSE message which includes an updated lower layer configuration, e.g., containing the CSI report configuration.

[0046] 7. The gNB-CU sends a UE CONTEXT MODIFICATION REQUEST message to the candidate gNB-DU(s) containing the CSI report configuration, TCI state information, RACH Configuration, and the LTM configuration IDs of the candidate cells in other candidate gNB-DU(s). The gNB-CU may also provide the lower layer part of the reference configuration to the candidate gNB-DU(s). The gNB-CU may also provide an updated CSI resource configuration to the candidate gNB-DU(s).

[0047] 8. The candidate gNB-DU responds with a UE CONTEXT MODIFICATION RESPONSE message including the updated lower layer configuration. The candidate gNB- DU may also respond the updated CSI report configuration.

[0048] 9. The gNB-CU sends a DL RRC MESSAGE TRANSFER message to the source gNB-DU, which includes the generated RRCReconfiguration message with the LTM configuration.

[0049] 10. The source gNB-DU forwards the received RRCReconfiguration message to theUE.

[0050] 11. The UE responds to the source gNB-DU with an RRCReconfigurationComplete message.

[0051] 12. The source gNB-DU forwards the RRCReconfigurationComplete message to the gNB-CU via an UL RRC MESSAGE TRANSFER message.

[0052] 13. Early synchronization may be performed as specified in TS 38.300. One way to perform early synchronization is by sending to the UE a PDCCH order indicating to it to perform RACH to the target cell of the candidate gNB-DU. Then candidate gNB-DU calculates the TA value for this UE.

[0053] 14 - 15. The candidate gNB-DU sends the TA value, the associated CFRA resource information, the candidate cell ID and the source gNB-DU ID to the source gNB-DU via the DU-CU TA INFORMATION TRANSFER and CU-DU TA INFORMATION TRANSFER messages, for which the source gNB-DU ID is omitted in the CU-DU TA INFORMATION TRANSFER message.

[0054] 16. The UE sends the LI measurement result to the source gNB-DU.

[0055] 17. The source gNB-DU decides to execute LTM to a candidate target cell.

[0056] 18. The source gNB-DU sends the Cell Switch command to the UE.

[0057] 19. The source gNB-DU sends the DU-CU CELL SWITCH NOTIFICATION message to the gNB-CU to indicate the initiation of the Cell Switch command to the UE, for which the message includes the target cell ID and the TCI state ID.

[0058] 20. The gNB-CU forwards the target cell ID and the TCI state ID to the target gNB- DU in the CU-DU CELL SWITCH NOTIFICATION message.

[0059] 21. The target gNB-DU detects the UE access using its first uplink transmission.

[0060] 22. The target gNB-DU sends the ACCESS SUCCESS message to the gNB-CU with the target cell ID.

[0061] 23. The UE sends an RRCReconfigurationComplete message to the target gNB-DU.

[0062] 24. The target gNB-DU forwards the RRCReconfigurationComplete message to the gNB-CU via an UL RRC MESSAGE TRANSFER message.

[0063] 25. The gNB-CU may send the UE CONTEXT RELEASE COMMAND message to the source gNB-DU to release the resources of prepared cells.

[0064] 26. The source gNB-DU responds with a UE CONTEXT RELEASE COMPLETE message.

[0065] Ll / 2 Triggered Mobility - with CU-UP change

[0066] In order to capture the interactions for data forwarding, FIG. 3 shows the CU-CP and CU-UP interactions. The UE is not shown to make FIG. 3 more readable. FIG. 3 shows steps 0-20, and the signaling exchange between the source gNB-DU 310, target gNB-DU 320, gNB-CU-CP 330, source gNB-CU-UP 340, target gNB-CU-UP 350, and AMF / UPF 190:

[0067] 0. The source gNB-DU forwards the Measurement Report to the gNB-CU-CP.

[0068] 1. The gNB-CU-CP decides to initiate LTM configuration.

[0069] 2. The gNB-CU-CP sends a BEARER CONTEXT SETUP REQUEST message containing UL TNL address information for NG-U to set up the bearer context in the target gNB-CU-UP.

[0070] 3. The target gNB-CU-UP responds with a BEARER CONTEXT SETUP RESPONSE message containing the UL TNL address information for Fl -U, DL TNL address information for NG-U, and the TNL address information for data forwarding to the target gNB-CU-UP.

[0071] 4. LTM configuration procedures are performed between gNB-CU and candidate gNB-DUs, and between gNB-CU and source gNB-DU as specified from step 3 to step 8 in section 8.2.1.5.

[0072] 5 - 6. The gNB-CU-CP sends the RRC Reconfiguration message to the UE.

[0073] 7. The UE sends the lower layer measurement result to the source gNB-DU, and the source gNB-DU decides to execute LTM to a candidate target cell.

[0074] 8. The source gNB-DU sends the DU-CU CELL SWITCH NOTIFICATIONmessage to the gNB-CU-CP with the selected target cell ID.

[0075] 9 -10. The gNB-CU-CP performs the Bearer Context Modification procedure to retrieve the PDCP UL / DL status and to exchange the TNL address information for data forwarding for the bearers.

[0076] 11 -12. The gNB-CU-CP performs the Bearer Context Modification procedure to send the DL TNL address information for Fl-U and the PDCP UP / DL status to the target gNB-CU-UP.

[0077] 13. Data Forwarding may be performed from the source gNB-CU-UP to the target gNB-CU-UP.

[0078] 14. The target gNB-DU detects the UE in the target cell.

[0079] 15. The target gNB-DU sends an ACCESS SUCCESS message to the gNB-CU-CP.

[0080] 16-18. Path Switch procedure is performed to update the DL TNL address information for the NG-U towards the core network.

[0081] 19-20. Bearer Context Release procedure may be performed to release the UE context in the source gNB-DU.

[0082] Rel .19 WID

[0083] From the Rel .19 Mobility WID :

[0084] According to the above description it is clear that a goal is to specify in Rel.19 the inter CU LTM relevant procedures to reduce the handover latency and interruption time.

[0085] One procedure is based on so-called “on-time” data forwarding. That is, data forwarding is triggered when LTM CELL CHANGE NOTIFICATION message is sent from gNB-DU to gNB-CU. This can be the baseline procedure without early TA acquisition.

[0086] However, with early TA acquisition, the initial access procedure after cell change trigger can be avoided. Further, the motivation behind early TA acquisition is to reduce the handover interruption time. Nonetheless, if data forwarding is also not performed early, it may again result in larger interruption time than needed.”

[0087] Differences from the examples described herein include the following (1-4): 1) The above (e.g. on-time data forwarding) hints the initiation of data forwarding in relation to early TA acquisition but it does not mention this specifically, 2) In the examples described herein other possible triggers can be considered, e.g., TCI state activation, 3) The termination of the data forwarding is not considered at all in e.g. on time data forwarding, 4) The above idea (e.g. on-time data forwarding) does not discuss the possibility to end early data forwarding based on other triggers - as the ones considered and described herein.

[0088] On time data forwarding is considered in 3GPP. Additionally, it is possible to start data forwarding earlier than “on time data forwarding”. Differences from the examples described herein include that on time data forwarding does not consider the triggers described herein, and the termination of the data forwarding is not considered at all.

[0089] In LTM Rel.18 we have the following data forwarding options (early data forwarding, on time data forwarding, and late data forwarding):

[0090] Early Data Forwarding: in this option, the data forwarding starts at the time of preparation. Specifically, the source initiates the data forwarding to the target cell once the preparation is finalized. The challenges with early data forwarding include that 1) data forwarding goes to all prepared cells resulting in a waste of resources. For example, if 8 candidates are configured for LTM, the preparation would require data forwarding to each of the candidate cells, per UE. This would cause a large amount of wasted resources on the network side, and 2) the network stops data forwarding when the cell switch is triggered.

[0091] On time Data Forwarding: in this option, the data forwarding starts at the time of the cell change of the source cell - this is triggered by the cell switch notification. The challenge with on time data forwarding is that it is better than early, since the data goes only in one cell but it still may arrive slightly late, due to data forwarding triggering at the same time like the cell change triggering.

[0092] Late Data Forwarding: in this option, the data forwarding starts after the completion of the handover. Practically, the source starts forwarding the packets to the target once the handover is finalized. Challenges with late data forwarding are that (i-ii): i) Data forwarding starts late resulting in delays, and 1) network needs to buffer the data while UE is having an interruption 2) depending on implementation, this may cause delays due to retransimissions, ii) With a tight packet delay budget (PDB), the forwarded packet may be too old to be usable and is discarded. For instance, with low latency services.

[0093] The previous description can lead to the following problem formulation: When, and based on which input(s), the network should start data forwarding, and When and how to stop earlier data forwarding.

[0094] Solution 1: Defining a new trigger for early data forwarding

[0095] The source gNB does not trigger early data forwarding upon preparation, but another trigger is used. In this case Data forwarding starts (or restarts) with other triggers than that of the cell switch command as (1-3): 1) Network triggered PDCCH ordered RACH with candidateld, 2) Network triggered TCI state activation MAC CE containing candidateld, 3) UE transmitted L3 / LI measurement report. When the L3 / L1 RSRP thresholds is triggering cell switch / Early TCI activation / Early TA acquisition or activation / Ll-RSRP measurements, the network starts early data forwarding.

[0096] Solution 2: In case of early data forwarding

[0097] The source starts data forwarding early, at the time of preparation. However, we enable data forwarding to stop when a stopping condition is triggered in the DU, i.e., TA validity expiry, TCI state de-activation, cell switch command. Solution 2 is applicable also for cases when data forwarding has been triggered in case of solution 1.

[0098] Solution 1

[0099] FIG. 4 and FIG. 5 present solution 1 briefly described above for two triggering events, a) TCI state activation, and b) TA acquisition triggering. Specifically steps 1-28 in FIG. 4 include the following, where FIG. 4 shows the signaling exchange between the UE 110, source DU 410, CU-CP_S 420, CU-CP_T 430, source CU-UP 440, and target DU 450:

[0100] Steps 1-3: UE provides L3 measurements to the CU-CP source. The latter, based on the L3 measurements proceeds in LTM HO decision.

[0101] Steps 4-7: Source CU-CP sends an LTM handover request to the target CU-CP. Target communicates with the Target DUs and to perform UE context Setup.

[0102] Steps 8-10: Source CU-CP performs UE context modification with the source DU to obtain TCI state configurations and also share the target cell configurations with the source DU.

[0103] Steps 11-14: Source CU-CP provides the RRC configurations with the UE.

[0104] Steps 15-22: UE starts providing LI measurement reports (e.g., periodic reports). Based on these reports the Source DU may trigger early TA acquisition. The UE performs RACH to obtain the target cell TA value, which is maintained by the network.

[0105] Steps 23-25: UE provides LI measurement reports (periodically); network decides to activate TCI states from the target cell and does so using a MAC CE.

[0106] Step 26-27: Source DU informs Source CU-CP to initiate data forwarding, indicating as trigger the TCI state activation. CU-CP triggers bearer context modification to the source CU-UP (with a UE context modification request and the respective response).

[0107] Step 28: Procedure is finalized as per standard LTM.

[0108] TA based data forwarding triggering is similar to the solution described above. Specifically FIG. 5 shows steps 1-28, including the signaling exchange between UE 110, source DU 510, CU-CP_S 520, CU-CP_T 530, source CU-UP 540, and target DU 550:

[0109] Steps 1-3: UE provides L3 measurements to the CU-CP source. The latter, based on the L3 measurements proceeds in LTM HO decision.

[0110] Steps 4-7: Source CU-CP sends an LTM handover request to the target CU-CP. Target communicates with the Target DUs and to perform UE context Setup.

[0111] Steps 8-10: Source CU-CP performs UE context modification with the source DU to obtain TCI state configurations and also share the target cell configurations with the source DU.

[0112] Steps 11-14: Source CU-CP provides the RRC configurations with the UE.

[0113] Steps 15-17: UE starts providing LI measurement reports (periodic reports). Based on these reports the Source DU may trigger early TA acquisition.

[0114] Step 18-19: Upon triggering early TA acquisition the source DU informs Source CU-CP to initiate data forwarding. CU-CP triggers bearer context modification to the source CU-UP (with a UE context modification request and the respective response).

[0115] Steps 20-24: The UE performs RACH to obtain the target cell TA value, which is maintained by the network.

[0116] Steps 25-27: UE provides LI measurement reports (periodically); network decides to activate TCI states from the target cell and does so using a MAC CE.

[0117] Step 28: Procedure is finalized as per standard LTM.

[0118] In one embodiment, the network receives periodical L3 measurement reports from the UE. Upon receiving L3 measurement report, and when the RSRP / RSRQ value of the serving cell / candidate cell is above / below a threshold, the network triggers data forwarding from CU-CP where the L3 report was received to CU-CP indicated by the L3 measurement report.

[0119] In the current LTM design the DU is making the handover decision. However, in the network, this may also be implemented in such way that the CU is making the final handover decision, and DU is following the signaling from the associated CU. Regardless of which solution is implemented, the network may decide to implement time based early data forwarding. In this case, referring to FIG. 6, once the network (such as source CU / DU 610) has made the decision at 630 to trigger the cell switch to the target CU-CP 620, the network (such as source CU / DU 610) may delay the message 660 towards UE 110 by X milliseconds (as indicated at 650), and at 640 start the data forwarding X ms before the handover trigger 660 is transmitted. The X may be a network internally configured value. One example is shown in the FIG. 6. Thus FIG. 6 shows an example using L3 measurement report.

[0120] Solution 2:

[0121] FIG. 7 presents solution 2 briefly described above. Steps 1-33 in FIG. 7 are as follows, where FIG. 7 shows the signaling exchange between UE 110, source DU 710, CU- CP_S 720, CU-CP T 730, source CU-UP 740, and target DU 750:

[0122] Steps 1-3: UE provides L3 measurements to the CU-CP source. The latter, based on the L3 measurements proceeds in LTM HO decision.

[0123] Steps 4-7: Source CU-CP sends an LTM handover request to the target CU-CP. Target communicates with the Target DUs and to perform UE context Setup.

[0124] Steps 8-10: Source CU-CP performs UE context modification with the source DU to obtain TCI state configurations and also share the target cell configurations with the source DU.

[0125] Steps 11-15: Source CU-CP provides the RRC configurations with the UE. In step 12 the source CU-CP may initiate the data forwarding to the target.

[0126] Steps 16-24: UE starts providing LI measurement reports (periodic reports). Basedon these reports the Source DU may trigger early TA acquisition. The UE performs RACH to obtain the target cell TA value, which is maintained by the network.

[0127] Steps 24-26: UE provides LI measurement reports (periodically); network decides to activate TCI states from the target cell and does so using a MAC CE.

[0128] Step 27-29: Base on periodic LI measurement reports the source DU may decide to deactivate some TCI states for a certain target cell and does so using a MAC CE (MAC CE message indicates the activated TCI states).

[0129] Step 30: Source DU indicates to Source CU-CP that it has de-activated a TCI state for a certain target cell which Data forwarding has been active. The deactivation message trigger toward CU-CP may be explicit deactivation command towards UE (e.g. MAC CE with TCI deactivation bit has been transmitted), or the trigger towards CU-CP can be triggered by transmitting additional TCI activation command to UE, which implicitly deactivates the not indicated TCI states in the UE’s active TCI state list. In other words, the network will send a message towards UE and before / after it transmits message from DU to CU-CP.

[0130] Step 31-33: Source CU-CP de-activates data forwarding and informs Target CU-CP about this deactivation.

[0131] In some embodiments, the de-activation of data forwarding can happen for other reasons as well, e.g., TA validity expiration, cell switch command, or based on target cell measurements from LI report (for example step 27 in FIG. 7) in the source DU.

[0132] Additionally, de-activation on certain targets can happen in case TA acquisition is triggered for a cell. In this case the CU will have started early data forwarding to multiple cells and the DU will send to the CU that the TA acquisition is triggered to a specific cell and the CU will stop the data forwarding to all the cells except the one that the TA acquisition is triggered.

[0133] The Solution 2 is applicable not only for early data forwarding but for Solution 1 as well.

[0134] Standardized messages may be exchanged in Xn and Fl interfaces. The examples described herein may be relevant to TS38.401.

[0135] FIG. 8 is an example apparatus 800, which may be implemented in hardware, configured to implement the examples described herein. The apparatus 800 comprises at least one processor 802 (e.g. an FPGA and / or CPU), one or more memories 804 including computer program code 805, the computer program code 805 having instructions to carry out the methods described herein, wherein the at least one memory 804 and the computer program code 805 are configured to, with the at least one processor 802, cause the apparatus 800 to implement circuitry, a process, component, module, or function (implemented with control module 806) to implement the examples described herein. The one or more memories 804 may include a non-transitory memory, a transitory memory, a volatile memory (e.g. RAM), or a non-volatile memory (e.g. ROM).

[0136] Forwarding trigger 830 implements the examples described herein related to not so early data forwarding.

[0137] The apparatus 800 includes a display and / or I / O interface 808, which includes user interface (UI) circuitry and elements, that may be used to display aspects or a status of the methods described herein (e.g., as one of the methods is being performed or at a subsequent time), or to receive input from a user such as with using a keypad, camera, touchscreen, touch area, microphone, biometric recognition, one or more sensors, etc. The apparatus 800 includes one or more communication e.g. network (N / W) interfaces (I / F(s)) 810. The communication I / F(s) 810 may be wired and / or wireless and communicate over the Internet / other network(s) via any communication technique including via one or more links 824. The link(s) 824 may be the link(s) 131 and / or 176 from FIG. 1. The link(s) 131 and / or 176 from FIG. 1 may also be implemented using transceiver(s) 816 and corresponding wireless link(s) 826. The communication I / F(s) 810 may comprise one or more transmitters or one or more receivers.

[0138] The transceiver 816 comprises one or more transmitters 818 and one or more receivers 820. The transceiver 816 and / or communication I / F(s) 810 may comprise standard well-known components such as an amplifier, filter, frequency-converter, (de)modulator, and encoder / decoder circuitries and one or more antennas, such as antennas 814 used for communication over wireless link 826.

[0139] The control module 806 of the apparatus 800 comprises one of or both parts 806-1 and / or 806-2, which may be implemented in a number of ways. The control module 806 maybe implemented in hardware as control module 806-1, such as being implemented as part of the one or more processors 802. The control module 806-1 may be implemented also as an integrated circuit or through other hardware such as a programmable gate array. In another example, the control module 806 may be implemented as control module 806-2, which is implemented as computer program code (having corresponding instructions) 805 and is executed by the one or more processors 802. For instance, the one or more memories 804 store instructions that, when executed by the one or more processors 802, cause the apparatus 800 to perform one or more of the operations as described herein. Furthermore, the one or more processors 802, the one or more memories 804, and example algorithms (e.g., as flowcharts and / or signaling diagrams), encoded as instructions, programs, or code, are means for causing performance of the operations described herein.

[0140] The apparatus 800 to implement the functionality of control 806 may be UE 110, RAN node 170 (e.g. gNB), or network element(s) 190 (e.g. LMF 190). Thus, processor 802 may correspond to processor(s) 120, processor(s) 152 and / or processor(s) 175, memory 804 may correspond to one or more memories 125, one or more memories 155 and / or one or more memories 171, computer program code 805 may correspond to computer program code 123, computer program code 153, and / or computer program code 173, control module 806 may correspond to module 140-1, module 140-2, module 150-1, and / or module 150-2, and communication I / F(s) 810 and / or transceiver 816 may correspond to transceiver 130, antenna(s) 128, transceiver 160, antenna(s) 158, N / W I / F(s) 161, and / or N / W I / F(s) 180. Alternatively, apparatus 800 and its elements may not correspond to either of UE 110, RAN node 170, or network element(s) 190 and their respective elements, as apparatus 800 may be part of a self-organizing / optimizing network (SON) node or other node, such as a node in a cloud. Apparatus 800 may correspond to any of the other apparatuses described herein.

[0141] The apparatus 800 may also be distributed throughout the network (e.g. 100) including within and between apparatus 800 and any network element (such as a network control element (NCE) 190 and / or the RAN node 170 and / or UE 110).

[0142] Interface 812 enables data communication and signaling between the various items of apparatus 800, as shown in FIG. 8. For example, the interface 812 may be one or more buses such as address, data, or control buses, and may include any interconnection mechanism, such as a series of lines on a motherboard or integrated circuit, fiber optics or other optical communication equipment, and the like. Computer program code (e.g.instructions) 805, including control 806 may comprise object-oriented software configured to pass data or messages between objects within computer program code 805, or computer program code (e.g. instructions) 805, including control 806 may include functional, scripting, or procedural code. The apparatus 800 need not comprise each of the features mentioned, or may comprise other features as well. The various components of apparatus 800 may at least partially reside in a common housing 828, or a subset of the various components of apparatus 800 may at least partially be located in different housings, which different housings may include housing 828.

[0143] FIG. 9 shows a schematic representation of non-volatile memory media 900a (e.g. computer / compact disc (CD) or digital versatile disc (DVD)) and 900b (e.g. universal serial bus (USB) memory stick) and 900c (e.g. cloud storage for downloading instructions and / or parameters 902 or receiving emailed instructions and / or parameters 902) storing instructions and / or parameters 902 which when executed by a processor allows the processor to perform one or more of the steps of the methods described herein. Instructions and / or parameters 902 may represent a non-transitory computer readable medium.

[0144] FIG. 10 is an example method 1000 based on the examples described herein. At 1010, the method includes determining whether to transmit one of: an indication to initiate data forwarding, or an indication to stop data forwarding. At 1020, the method includes transmitting, to a network entity, one of: the indication to initiate data forwarding, or the indication to stop data forwarding. Method 1000 may be performed with RAN node 170, DU 195, source gNB-DU 210, source gNB-DU 310, source DU 410, source DU 510, source DU 610, source DU 710, or apparatus 800.

[0145] FIG. 11 is an example method 1100 based on the examples described herein. At 1110, the method includes receiving, from a network entity, one of: an indication to initiate data forwarding, or an indication to stop data forwarding. At 1120, the method includes performing one of: transmitting a bearer context modification request in response to receiving from the network entity the indication to initiate data forwarding, or stopping data forwarding in response to receiving from the network entity the indication to stop data forwarding. Method 1100 may be performed with RAN node 170, CU 196, gNB-CU 230, gNB-CU-CP 330, CU-CP_S 420, CU-CP_S 520, source CU 610, CU-CP_S 720, or apparatus 800.

[0146] FIG. 12 is an example method 1200 based on the examples described herein. At1210, the method includes receiving, from a network entity, a handover request. At 1220, the method includes receiving, from the network entity, an indication of a stopping of data forwarding. At 1230, the method includes wherein the indication of the stopping of data forwarding is based on transmission configuration indicator state deactivation, a timing advance validity expiration, a cell switch command, target cell measurements from a layer 1 report, or a triggering of a timing advance acquisition. Method 1200 may be performed with RAN node 170, CU 196, gNB-CU 230, CU-CP_T 430, CU-CP_T 530, target CU-CP 620, CU-CP T 730, or apparatus 800.

[0147] FIG. 13 is an example method 1300 based on the examples described herein. At 1310, the method includes transmitting, to a network entity, a measurement report. At 1320, the method includes wherein the measurement report is configured to be used with the network entity to determine whether to initiate data forwarding or stop data forwarding. AT 1330, the method includes receiving, from the network entity, an indication related to the determination of whether to initiate data forwarding or stop data forwarding. Method 1300 may be performed with UE 110 or apparatus 800.

[0148] FIG. 14 is an example method 1400 based on the examples described herein. At 1410, the method includes receiving, from a network entity, a bearer context modification request comprising an indication to initiate data forwarding. At 1420, the method includes wherein the bearer context modification request comprising the indication to initiate data forwarding is based on one of: transmission configuration indicator state activation, early timing advance acquisition, a physical downlink control channel ordered random access channel, or a layer 3 measurement report that indicates that a reference signal received power or reference signal received quality value of a serving cell or candidate cell is above or below a threshold. At 1430, the method includes initiating data forwarding, based on the bearer context modification request comprising the indication to initiate data forwarding received from the network entity. Method 1400 may be performed with RAN node 170, CU 196, gNB- CU 230, source gNB-CU-UP 340, source CU-UP 440, source CU-UP 540, source CU 610, source CU-UP 740, or apparatus 800.

[0149] The following examples are provided and described herein.

[0150] Example 1. An 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 atleast to: determine whether to transmit one of: an indication to initiate data forwarding, or an indication to stop data forwarding; and transmit, to a network entity, one of: the indication to initiate data forwarding, or the indication to stop data forwarding.

[0151] Example 2. The apparatus of example 1, wherein the indication to initiate data forwarding is transmitted based on a trigger other than a cell switch command.

[0152] Example 3. The apparatus of any of examples 1 to 2, wherein the instructions, when executed by the at least one processor, cause the apparatus at least to: receive, from a user equipment, a layer 1 measurement report; determine to activate a transmission configuration indicator state, based on the layer 1 measurement report received from the user equipment; and transmit, to the network entity, the indication to initiate data forwarding, in response to determining to activate the transmission configuration indicator state.

[0153] Example 4. The apparatus of example 3, wherein the instructions, when executed by the at least one processor, cause the apparatus at least to: transmit, to the user equipment, a medium access control control element comprising: a transmission configuration indicator state activation command, and a candidate identifier associated with a target cell; wherein the medium access control control element comprising the transmission configuration indicator state activation command and the candidate identifier associated with the target cell triggers the transmitting of the indication to the network entity to initiate data forwarding, wherein the network entity comprises a source central unit.

[0154] Example 5. The apparatus of any of examples 1 to 4, wherein the instructions, when executed by the at least one processor, cause the apparatus at least to: receive, from a user equipment, a layer 1 measurement report; determine to trigger early timing advance acquisition, based on the layer 1 measurement report received from the user equipment; and transmit, to the network entity, the indication to initiate data forwarding, in response to determining to trigger early timing advance acquisition.

[0155] Example 6. The apparatus of example 5, wherein the instructions, when executed by the at least one processor, cause the apparatus at least to: transmit, to a user equipment, a physical downlink control channel ordered random access channel with a candidate identifier associated with a target cell; wherein the physical downlink control channel ordered random access channel with the candidate identifier associated with the target cell triggers the transmitting of the indication to the network entity to initiate data forwarding, wherein thenetwork entity comprises a source central unit.

[0156] Example 7. The apparatus of any of examples 1 to 6, wherein the instructions, when executed by the at least one processor, cause the apparatus at least to: receive, from a user equipment, periodic layer 3 measurement reports; and trigger data forwarding from a control unit control plane, in response to receiving a layer 3 measurement report, and when a reference signal received power or reference signal received quality value of a serving cell or candidate cell is above or below a threshold.

[0157] Example 8. The apparatus of any of examples 1 to 7, wherein the instructions, when executed by the at least one processor, cause the apparatus at least to: determine to deactivate a transmission configuration indicator state for a target cell; and transmit, to the network entity, the indication to stop data forwarding, in response to determining to deactivate the transmission configuration indicator state for the target cell.

[0158] Example 9. The apparatus of example 8, wherein the instructions, when executed by the at least one processor, cause the apparatus at least to: transmit, to the network entity, an indication of the deactivation of the transmission configuration indicator state for the target cell; wherein the indication of the deactivation of the transmission configuration indicator state for the target cell transmitted to the network entity comprises the indication to stop data forwarding.

[0159] Example 10. The apparatus of example 9, wherein the instructions, when executed by the at least one processor, cause the apparatus at least to: transmit, to a user equipment, a medium access control control element comprising a command to deactivate the transmission configuration indicator state; wherein the deactivation of the transmission configuration indicator state is performed with transmitting the medium access control control element for an activation of transmission configuration indicator states without including a transmission configuration indicator state that has been activated before, wherein the transmission configuration indicator state that has been activated before is the transmission configuration indicator state that is deactivated; wherein the indication of the deactivation of the transmission configuration indicator state for the target cell transmitted to the network entity is based on the medium access control control element transmitted to the user equipment for the activation of the transmission configuration indicator states without including the transmission configuration state that has been activated before that is deactivated.

[0160] Example 11. The apparatus of any of examples 9 to 10, wherein the instructions, when executed by the at least one processor, cause the apparatus at least to: transmit, to a user equipment, a command to deactivate a transmission configuration indicator state before or after transmitting, to the network entity, the indication of the deactivation of the transmission configuration indicator state for the target cell; wherein the deactivation of the transmission configuration indicator state is performed with transmitting the command for an activation of transmission configuration indicator states without including a transmission configuration indicator state that has been activated before, wherein the transmission configuration indicator state that has been activated before is the transmission configuration indicator state that is deactivated; wherein the indication of the deactivation of the transmission configuration indicator state for the target cell transmitted to the network entity is based on the command transmitted to the user equipment for the activation of the transmission configuration indicator states without including the transmission configuration state that has been activated before that is deactivated.

[0161] Example 12. The apparatus of any of examples 8 to 11, wherein the instructions, when executed by the at least one processor, cause the apparatus at least to: receive, from a user equipment, a layer 1 measurement report; wherein the determining to deactivate the transmission configuration indicator state for the target cell is based on the layer 1 measurement report received from the user equipment.

[0162] Example 13. The apparatus of any of examples 1 to 12, wherein the instructions, when executed by the at least one processor, cause the apparatus at least to: transmit, from the apparatus to a source control unit control plane, an indication of the stopping of the data forwarding, wherein the apparatus comprises a source distributed unit.

[0163] Example 14. The apparatus of any of examples 1 to 13, wherein the instructions, when executed by the at least one processor, cause the apparatus at least to: determine a timing advance validity expiration, a cell switch command, target cell measurements from a layer 1 report, or to trigger timing advance acquisition; and transmit, to the network entity, the indication to stop data forwarding, in response to determining the timing advance validity expiration, the cell switch command, the target cell measurements from a layer 1 report, or to trigger the timing advance acquisition.

[0164] Example 15. The apparatus of any of examples 1 to 14, wherein the instructions,when executed by the at least one processor, cause the apparatus at least to: determine to trigger timing advance acquisition for a cell; and transmit, to a central unit, an indication that the timing advance acquisition for the cell is triggered; wherein the indication that the timing advance acquisition for the cell is triggered that is transmitted to the central unit comprises an indication to stop data forwarding to cells except for the cell for which the timing advance acquisition is triggered.

[0165] Example 16. The apparatus of any of examples 1 to 15, wherein the instructions, when executed by the at least one processor, cause the apparatus at least to: determine to switch a user equipment from a source cell to a target cell; delay transmitting a cell switch command to the user equipment with an amount of time; start data forwarding towards a network entity that provides access to a target cell with the amount of time before transmitting the cell switch command to the user equipment; and transmit the cell switch command to the user equipment with the amount of time after starting the data forwarding towards the network entity that provides access to the target cell.

[0166] Example 17. The apparatus of any of examples 1 to 16, wherein the apparatus comprises a source distributed unit, and the network entity comprises a source control unit control plane.

[0167] Example 18. The apparatus of any of examples 1 to 17, wherein the apparatus comprises the network entity.

[0168] Example 19. An 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 at least to: receive, from a network entity, one of: an indication to initiate data forwarding, or an indication to stop data forwarding; and perform one of: transmit a bearer context modification request in response to receiving from the network entity the indication to initiate data forwarding, or stop data forwarding in response to receiving from the network entity the indication to stop data forwarding.

[0169] Example 20. The apparatus of example 19, wherein the indication to initiate data forwarding is received based on a trigger other than a cell switch command.

[0170] Example 21. The apparatus of any of examples 19 to 20, wherein the instructions, when executed by the at least one processor, cause the apparatus at least to: receive, from thenetwork entity, the indication to initiate data forwarding, based on a determination to activate a transmission configuration indicator state.

[0171] Example 22. The apparatus of any of examples 19 to 21, wherein the instructions, when executed by the at least one processor, cause the apparatus at least to: receive, from the network entity, the indication to initiate data forwarding, based on a determination to trigger early timing advance acquisition.

[0172] Example 23. The apparatus of example 22, wherein: a physical downlink control channel ordered random access channel is transmitted to a user equipment with a candidate identifier associated with a target cell; and the physical downlink control channel ordered random access channel transmitted to the user equipment with the candidate identifier associated with a target cell triggers the indication to initiate data forwarding.

[0173] Example 24. The apparatus of any of examples 19 to 23, wherein the instructions, when executed by the at least one processor, cause the apparatus at least to: receive, from a user equipment, periodic layer 3 measurement reports; and trigger data forwarding from a control unit control plane, in response to receiving a layer 3 measurement report, and when a reference signal received power or reference signal received quality value of a serving cell or candidate cell is above or below a threshold.

[0174] Example 25. The apparatus of any of examples 19 to 24, wherein the instructions, when executed by the at least one processor, cause the apparatus at least to: receive, from the network entity, the indication to stop data forwarding, based on a deactivation of a transmission configuration indicator state for a target cell.

[0175] Example 26. The apparatus of example 25, wherein the instructions, when executed by the at least one processor, cause the apparatus at least to: receive, from the network entity, an indication of the deactivation of the transmission configuration indicator state for the target cell; wherein the indication of the deactivation of the transmission configuration indicator state for the target cell received from the network entity comprises the indication to stop data forwarding.

[0176] Example 27. The apparatus of example 26, wherein the indication of the deactivation of the transmission configuration indicator state for the target cell received from the network entity is based on a medium access control control element comprising a command todeactivate the transmission configuration indicator state for the target cell.

[0177] Example 28. The apparatus of any of examples 26 to 27, wherein the indication of the deactivation of the transmission configuration indicator state for the target cell received from the network entity is based on a command to deactivate a transmission configuration indicator state.

[0178] Example 29. The apparatus of any of examples 25 to 28, wherein the deactivation of the transmission configuration indicator state for the target cell is based on a layer 1 measurement report of a user equipment.

[0179] Example 30. The apparatus of any of examples 19 to 29, wherein the instructions, when executed by the at least one processor, cause the apparatus at least to: transmit, to a target control unit control plane, an indication of the stopping of the data forwarding.

[0180] Example 31. The apparatus of any of examples 19 to 30, wherein the instructions, when executed by the at least one processor, cause the apparatus at least to: receive, from the network entity, the indication to stop data forwarding, based on a timing advance validity expiration, a cell switch command, or target cell measurements from a layer 1 report.

[0181] Example 32. The apparatus of any of examples 19 to 31, wherein the instructions, when executed by the at least one processor, cause the apparatus at least to: determine to trigger timing advance acquisition for a cell; and receive, from a distributed unit, an indication that timing advance acquisition for a cell is triggered; wherein the indication that the timing advance acquisition for the cell is triggered that is received from the distributed unit comprises an indication to stop data forwarding to cells except for the cell for which the timing advance acquisition is triggered.

[0182] Example 33. The apparatus of any of examples 19 to 32, wherein the instructions, when executed by the at least one processor, cause the apparatus at least to: determine to switch a user equipment from a source cell to a target cell; delay transmitting a cell switch command to the user equipment with an amount of time; initiate or start data forwarding towards a network entity that provides access to a target cell with the amount of time before transmitting the cell switch command to the user equipment; and transmit the cell switch command to the user equipment with the amount of time after starting the data forwarding towards the network entity that provides access to the target cell.

[0183] Example 34. The apparatus of any of examples 19 to 33, wherein the apparatus comprises a source control unit control plane, and the network entity comprises a source distributed unit.

[0184] Example 35. The apparatus of any of examples 19 to 34, wherein the apparatus comprises the network entity.

[0185] Example 36. An 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 at least to: receive, from a network entity, a handover request; and receive, from the network entity, an indication of a stopping of data forwarding; wherein the indication of the stopping of data forwarding is based on transmission configuration indicator state deactivation, a timing advance validity expiration, a cell switch command, target cell measurements from a layer 1 report, or a triggering of a timing advance acquisition.

[0186] Example 37. The apparatus of example 36, wherein the instructions, when executed by the at least one processor, cause the apparatus at least to: receive data forwarding from a source network entity with an amount of time before the source network entity transmits a cell switch command to a user equipment to switch to the apparatus, wherein the apparatus provides access to a target cell.

[0187] Example 38. The apparatus of example 37, wherein the network entity comprises the source control unit or the source distributed unit.

[0188] Example 39. The apparatus of any of examples 36 to 38, wherein the network entity comprises a source control unit control plane.

[0189] Example 40. The apparatus of any of examples 36 to 39, wherein the apparatus comprises a target control unit control plane.

[0190] Example 41. The apparatus of any of examples 36 to 40, wherein the instructions, when executed by the at least one processor, cause the apparatus at least to: receive, from the network entity, an indication that the timing advance acquisition for a cell is triggered; wherein the indication that the timing advance acquisition for the cell is triggered that is received from the network entity comprises an indication to stop data forwarding to cells except for the cell for which the timing advance acquisition is triggered.

[0191] Example 42. An 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 at least to: transmit, to a network entity, a measurement report; wherein the measurement report is configured to be used with the network entity to determine whether to initiate data forwarding or stop data forwarding; and receive, from the network entity, an indication related to the determination of whether to initiate data forwarding or stop data forwarding.

[0192] Example 43. The apparatus of example 42, wherein the measurement report comprises a layer 1 measurement report and is configured to cause the network entity to activate a transmission configuration indicator state that triggers the initiation of data forwarding.

[0193] Example 44. The apparatus of example 43, wherein the instructions, when executed by the at least one processor, cause the apparatus at least to: receive, from the network entity, a medium access control control element comprising: a transmission configuration indicator state activation command, and a candidate identifier associated with a target cell; wherein the medium access control control element comprising the transmission configuration indicator state activation command and the candidate identifier associated with the target cell triggers the initiation of data forwarding; wherein the indication related to the determination of whether to initiate data forwarding or stop data forwarding comprises the medium access control control element comprising the transmission configuration indicator state activation command and the candidate identifier associated with the target cell.

[0194] Example 45. The apparatus of any of examples 42 to 44, wherein the measurement report comprises a layer 1 measurement report and is configured to cause the network entity to trigger early timing advance acquisition that triggers the initiation of data forwarding.

[0195] Example 46. The apparatus of example 45, wherein the instructions, when executed by the at least one processor, cause the apparatus at least to: receive, from the network entity, a physical downlink control channel ordered random access channel with a candidate identifier associated with a target cell; wherein the physical downlink control channel ordered random access channel with the candidate identifier associated with the target cell triggers the initiating of data forwarding; wherein the indication related to the determination of whether to initiate data forwarding or stop data forwarding comprises the physical downlink control channel ordered random access channel with the candidate identifier associated with the targetcell.

[0196] Example 47. The apparatus of any of examples 42 to 46, wherein the instructions, when executed by the at least one processor, cause the apparatus at least to: transmit, to the network entity, periodic layer 3 measurement reports; and wherein the periodic layer 3 measurement reports are configured to cause the network entity to trigger data forwarding from a control unit control plane, when a reference signal received power or reference signal received quality value of a serving cell or candidate cell is above or below a threshold.

[0197] Example 48. The apparatus of any of examples 42 to 47, wherein the instructions, when executed by the at least one processor, cause the apparatus at least to: receive, from the network entity, a medium access control control element comprising a command to deactivate a transmission configuration indicator state; wherein the command to deactivate the transmission configuration indicator state is based on receiving the medium access control control element for an activation of transmission configuration indicator states without including a transmission configuration indicator state that has been activated before, wherein the transmission configuration indicator state that has been activated before is the transmission configuration indicator state that is deactivated; wherein the medium access control control element comprising the command to deactivate the transmission configuration indicator state triggers stopping of data forwarding; wherein the indication related to the determination of whether to initiate data forwarding or stop data forwarding received from the network entity comprises the medium access control control element comprising the command to deactivate the transmission configuration indicator state.

[0198] Example 49. The apparatus of any of examples 42 to 48, wherein the instructions, when executed by the at least one processor, cause the apparatus at least to: receive, from the network entity, a command to deactivate a transmission configuration indicator state; wherein the command to deactivate the transmission configuration indicator state is based on receiving the command for an activation of transmission configuration indicator states without including a transmission configuration indicator state that has been activated before, wherein the transmission configuration indicator state that has been activated before is the transmission configuration indicator state that is deactivated; wherein the command to deactivate the transmission configuration indicator state triggers stopping of data forwarding; wherein the indication related to the determination of whether to initiate data forwarding or stop data forwarding received from the network entity comprises the command to deactivatethe transmission configuration indicator state.

[0199] Example 50. The apparatus of any of examples 42 to 49, wherein the measurement report comprises a layer 1 measurement report and is configured to cause the network entity to deactivate a transmission configuration indicator state for the target cell, wherein the deactivation of the transmission configuration indicator state for the target cell triggers stopping of data forwarding.

[0200] Example 51. The apparatus of any of examples 42 to 50, wherein the apparatus comprises a user equipment, or a user equipment comprises the apparatus.

[0201] Example 52. The apparatus of any of examples 42 to 51, wherein the instructions, when executed by the at least one processor, cause the apparatus at least to: receive, from a source network entity, a cell switch command to switch to a target network entity; wherein the cell switch command is received an amount of time after the source network entity starts data forwarding to the target network entity.

[0202] Example 53. An 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 at least to: receive, from a network entity, a bearer context modification request comprising an indication to initiate data forwarding; wherein the bearer context modification request comprising the indication to initiate data forwarding is based on one of: transmission configuration indicator state activation, early timing advance acquisition, a physical downlink control channel ordered random access channel, or a layer 3 measurement report that indicates that a reference signal received power or reference signal received quality value of a serving cell or candidate cell is above or below a threshold; and initiate data forwarding, based on the bearer context modification request comprising the indication to initiate data forwarding received from the network entity.

[0203] Example 54. The apparatus of example 53, wherein the apparatus comprises a source central unit user plane, and the network entity comprises a source central unit control plane.

[0204] Example 55. A method including: determining whether to transmit one of: an indication to initiate data forwarding, or an indication to stop data forwarding; and transmitting, to a network entity, one of: the indication to initiate data forwarding, or the indication to stop data forwarding.

[0205] Example 56. A method including: receiving, from a network entity, one of: an indication to initiate data forwarding, or an indication to stop data forwarding; and performing one of: transmitting a bearer context modification request in response to receiving from the network entity the indication to initiate data forwarding, or stopping data forwarding in response to receiving from the network entity the indication to stop data forwarding.

[0206] Example 57. A method including: receiving, from a network entity, a handover request; and receiving, from the network entity, an indication of a stopping of data forwarding; wherein the indication of the stopping of data forwarding is based on transmission configuration indicator state deactivation, a timing advance validity expiration, a cell switch command, target cell measurements from a layer 1 report, or a triggering of a timing advance acquisition.

[0207] Example 58. A method including: transmitting, to a network entity, a measurement report; wherein the measurement report is configured to be used with the network entity to determine whether to initiate data forwarding or stop data forwarding; and receiving, from the network entity, an indication related to the determination of whether to initiate data forwarding or stop data forwarding.

[0208] Example 59. A method including: receiving, from a network entity, a bearer context modification request comprising an indication to initiate data forwarding; wherein the bearer context modification request comprising the indication to initiate data forwarding is based on one of: transmission configuration indicator state activation, early timing advance acquisition, a physical downlink control channel ordered random access channel, or a layer 3 measurement report that indicates that a reference signal received power or reference signal received quality value of a serving cell or candidate cell is above or below a threshold; and initiating data forwarding, based on the bearer context modification request comprising the indication to initiate data forwarding received from the network entity.

[0209] Example 60. An apparatus including: means for determining whether to transmit one of: an indication to initiate data forwarding, or an indication to stop data forwarding; and means for transmitting, to a network entity, one of: the indication to initiate data forwarding, or the indication to stop data forwarding.

[0210] Example 61. An apparatus including: means for receiving, from a network entity, one of: an indication to initiate data forwarding, or an indication to stop data forwarding; andmeans for performing one of: transmitting a bearer context modification request in response to receiving from the network entity the indication to initiate data forwarding, or stopping data forwarding in response to receiving from the network entity the indication to stop data forwarding.

[0211] Example 62. An apparatus including: means for receiving, from a network entity, a handover request; and means for receiving, from the network entity, an indication of a stopping of data forwarding; wherein the indication of the stopping of data forwarding is based on transmission configuration indicator state deactivation, a timing advance validity expiration, a cell switch command, target cell measurements from a layer 1 report, or a triggering of a timing advance acquisition.

[0212] Example 63. An apparatus including: means for transmitting, to a network entity, a measurement report; wherein the measurement report is configured to be used with the network entity to determine whether to initiate data forwarding or stop data forwarding; and means for receiving, from the network entity, an indication related to the determination of whether to initiate data forwarding or stop data forwarding.

[0213] Example 64. An apparatus including: means for receiving, from a network entity, a bearer context modification request comprising an indication to initiate data forwarding; wherein the bearer context modification request comprising the indication to initiate data forwarding is based on one of: transmission configuration indicator state activation, early timing advance acquisition, a physical downlink control channel ordered random access channel, or a layer 3 measurement report that indicates that a reference signal received power or reference signal received quality value of a serving cell or candidate cell is above or below a threshold; and means for initiating data forwarding, based on the bearer context modification request comprising the indication to initiate data forwarding received from the network entity.

[0214] Example 65. A computer readable medium including instructions stored thereon for performing at least the following: determining whether to transmit one of: an indication to initiate data forwarding, or an indication to stop data forwarding; and transmitting, to a network entity, one of: the indication to initiate data forwarding, or the indication to stop data forwarding.

[0215] Example 66. A computer readable medium including instructions stored thereon forperforming at least the following: receiving, from a network entity, one of: an indication to initiate data forwarding, or an indication to stop data forwarding; and performing one of: transmitting a bearer context modification request in response to receiving from the network entity the indication to initiate data forwarding, or stopping data forwarding in response to receiving from the network entity the indication to stop data forwarding.

[0216] Example 67. A computer readable medium including instructions stored thereon for performing at least the following: receiving, from a network entity, a handover request; and receiving, from the network entity, an indication of a stopping of data forwarding; wherein the indication of the stopping of data forwarding is based on transmission configuration indicator state deactivation, a timing advance validity expiration, a cell switch command, target cell measurements from a layer 1 report, or a triggering of a timing advance acquisition.

[0217] Example 68. A computer readable medium including instructions stored thereon for performing at least the following: transmitting, to a network entity, a measurement report; wherein the measurement report is configured to be used with the network entity to determine whether to initiate data forwarding or stop data forwarding; and receiving, from the network entity, an indication related to the determination of whether to initiate data forwarding or stop data forwarding.

[0218] Example 69. A computer readable medium including instructions stored thereon for performing at least the following: receiving, from a network entity, a bearer context modification request comprising an indication to initiate data forwarding; wherein the bearer context modification request comprising the indication to initiate data forwarding is based on one of: transmission configuration indicator state activation, early timing advance acquisition, a physical downlink control channel ordered random access channel, or a layer 3 measurement report that indicates that a reference signal received power or reference signal received quality value of a serving cell or candidate cell is above or below a threshold; and initiating data forwarding, based on the bearer context modification request comprising the indication to initiate data forwarding received from the network entity.

[0219] References to a ‘computer’, ‘processor’, etc. should be understood to encompass not only computers having different architectures such as single / multi-processor architectures and sequential or parallel architectures but also specialized circuits such as field- programmable gate arrays (FPGAs), application specific circuits (ASICs), signal processingdevices and other processing circuitry. References to computer program, instructions, code etc. should be understood to encompass software for a programmable processor or firmware such as, for example, the programmable content of a hardware device whether instructions for a processor, or configuration settings for a fixed-function device, gate array or programmable logic device etc.

[0220] The memories as described herein may be implemented using any suitable data storage technology, such as semiconductor based memory devices, flash memory, magnetic memory devices and systems, optical memory devices and systems, non-transitory memory, transitory memory, fixed memory and removable memory. The memories may comprise a database for storing data.

[0221] The term “non-transitory,” as used herein, is a limitation of the medium itself (i.e., tangible, not a signal ) as opposed to a limitation on data storage persistency (e.g., RAM vs. ROM).

[0222] As used herein, the term ‘circuitry’ may refer to the following: (a) hardware circuit implementations, such as implementations in analog and / or digital circuitry, and (b) combinations of circuits and software (and / or firmware), such as (as applicable): (i) a combination of processor(s) or (ii) portions of processor(s) / software including digital signal processor(s), software, and memories that work together to cause an apparatus to perform various functions, and (c) circuits, such as a microprocessor(s) or a portion of a microprocessor(s), that require software or firmware for operation, even if the software or firmware is not physically present. As a further example, as used herein, the term ‘circuitry’ would also cover an implementation of merely a processor (or multiple processors) or a portion of a processor and its (or their) accompanying software and / or firmware. The term ‘circuitry’ would also cover, for example and if applicable to the particular element, a baseband integrated circuit or applications processor integrated circuit for a mobile phone or a similar integrated circuit in a server, a cellular network device, or another network device.

[0223] It should be understood that the foregoing description is only illustrative. Various alternatives and modifications may be devised by those skilled in the art. For example, features recited in the various dependent claims could be combined with each other in any suitable combination(s). In addition, features from different example embodiments described above could be selectively combined into a new example embodiment. Accordingly, thisdescription is intended to embrace all such alternatives, modifications and variances which fall within the scope of the appended claims.

[0224] The following acronyms and abbreviations that may be found in the specification and / or the drawing figures are given as follows (the abbreviations and acronyms may be appended / combined with each other or with other characters using e.g. a dash, hyphen, slash, letter, or number, and may be case insensitive):3 GPP third generation partnership project4G fourth generation5G fifth generation5GC 5G core networkAMF access and mobility management functionASIC application-specific integrated circuitCD compact / computer discCE control elementCFRA contention free random accessCPU central processing unitCSI channel state informationCU central unit or centralized unitCU-CP central unit control planeCU-CP S source CU-CPCU-CP T target CU-CPCU-UP central unit user planeDC dual connectivityDL downlinkDSP digital signal processorDU distributed unitDVD digital versatile disc eNB evolved Node B (e.g., an LTE base station)EN-DC E-UTRAN new radio - dual connectivity en-gNB node providing NR user plane and control plane protocol terminations towards the UE, and acting as a secondary node in EN- DCE-UTRA evolved UMTS terrestrial radio access, i.e., the LTE radio access technologyE-UTRAN E-UTRA networkF 1 interface between the CU and the DUFPGA field-programmable gate array gNB generalized node B, base station for 5G / NR, i.e., a node providingNR user plane and control plane protocol terminations towards the UE, and connected via the NG interface to the 5GCHO handoverIAB integrated access and backhaulID identifierI / F interfaceI / O input / outputLI layer 1Ll / 2 layer 1 and / or layer 2L2 layer 2L3 layer 3LMF location management functionLTE long term evolution (4G)LTM Ll / 2 triggered mobilityMAC medium access controlMAC CE medium access control control elementMCG master cell groupMME mobility management entityMN master nodeMRO mobility robustness optimizationNCE network control element ng or NG new generation ng-eNB new generation eNBNG-RAN new generation radio access networkNR new radioN / W networkPDA personal digital assistantPDB packet delay budgetPDCCH physical downlink control channelPDCP packet data convergence protocolPHY physical layerPRACH physical random access channelRACH random access channelRAM random access memoryRAN radio access networkRAN2 RAN WG2RAN3 RAN WG3Rel releaseRLC radio link controlRO RACH occasionROM read-only memoryRRC radio resource controlRSRP reference signal received powerRSRQ reference signal received qualityRU radio unitRx receive, or receiver, or receptionSA3 system aspects 3SCG secondary cell groupSDAP service data adaptation protocolSGW serving gatewaySMF session management functionSN secondary nodeSON self-organizing / optimizing networkTA timing advanceTCI transmission configuration indication or transmission configuration indicatorTNL transport network layerTRP transmission reception pointTS technical specificationTx transmit, or transmitter, or transmissionU user (e.g. Fl-U)UAV unmanned aerial vehicleUE user equipment (e.g., a wireless, typically mobile device)UI user interfaceUL uplinkUMTS Universal Mobile Telecommunications System UPF user plane functionUSB universal serial busWG working groupWID work item descriptionX2 network interface between RAN nodes and between RAN and the core networkXn network interface between NG-RAN nodes

Claims

CLAIMSWhat is claimed is:

1. An apparatus comprising: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus at least to: determine whether to transmit one of: an indication to initiate data forwarding, or an indication to stop data forwarding; and transmit, to a network entity, one of: the indication to initiate data forwarding, or the indication to stop data forwarding.

2. The apparatus of claim 1, wherein the indication to initiate data forwarding is transmitted based on a trigger other than a cell switch command.

3. The apparatus of any of claims 1 to 2, wherein the instructions, when executed by the at least one processor, cause the apparatus at least to: receive, from a user equipment, a layer 1 measurement report; determine to activate a transmission configuration indicator state, based on the layer 1 measurement report received from the user equipment; and transmit, to the network entity, the indication to initiate data forwarding, in response to determining to activate the transmission configuration indicator state.

4. The apparatus of claim 3, wherein the instructions, when executed by the at least one processor, cause the apparatus at least to: transmit, to the user equipment, a medium access control control element comprising: a transmission configuration indicator state activation command, and acandidate identifier associated with a target cell; wherein the medium access control control element comprising the transmission configuration indicator state activation command and the candidate identifier associated with the target cell triggers the transmitting of the indication to the network entity to initiate data forwarding, wherein the network entity comprises a source central unit.

5. The apparatus of any of claims 1 to 4, wherein the instructions, when executed by the at least one processor, cause the apparatus at least to: receive, from a user equipment, a layer 1 measurement report; determine to trigger early timing advance acquisition, based on the layer 1 measurement report received from the user equipment; and transmit, to the network entity, the indication to initiate data forwarding, in response to determining to trigger early timing advance acquisition.

6. The apparatus of claim 5, wherein the instructions, when executed by the at least one processor, cause the apparatus at least to: transmit, to a user equipment, a physical downlink control channel ordered random access channel with a candidate identifier associated with a target cell; wherein the physical downlink control channel ordered random access channel with the candidate identifier associated with the target cell triggers the transmitting of the indication to the network entity to initiate data forwarding, wherein the network entity comprises a source central unit.

7. The apparatus of any of claims 1 to 6, wherein the instructions, when executed by the at least one processor, cause the apparatus at least to: receive, from a user equipment, periodic layer 3 measurement reports; and trigger data forwarding from a control unit control plane, in response to receiving a layer 3 measurement report, and when a reference signal received power or reference signal received quality value of a serving cell or candidate cell is above orbelow a threshold.

8. The apparatus of any of claims 1 to 7, wherein the instructions, when executed by the at least one processor, cause the apparatus at least to: determine to deactivate a transmission configuration indicator state for a target cell; and transmit, to the network entity, the indication to stop data forwarding, in response to determining to deactivate the transmission configuration indicator state for the target cell.

9. The apparatus of claim 8, wherein the instructions, when executed by the at least one processor, cause the apparatus at least to: transmit, to the network entity, an indication of the deactivation of the transmission configuration indicator state for the target cell; wherein the indication of the deactivation of the transmission configuration indicator state for the target cell transmitted to the network entity comprises the indication to stop data forwarding.

10. The apparatus of claim 9, wherein the instructions, when executed by the at least one processor, cause the apparatus at least to: transmit, to a user equipment, a medium access control control element comprising a command to deactivate the transmission configuration indicator state; wherein the deactivation of the transmission configuration indicator state is performed with transmitting the medium access control control element for an activation of transmission configuration indicator states without including a transmission configuration indicator state that has been activated before, wherein the transmission configuration indicator state that has been activated before is the transmission configuration indicator state that is deactivated; wherein the indication of the deactivation of the transmission configuration indicator state for the target cell transmitted to the network entity is based on themedium access control control element transmitted to the user equipment for the activation of the transmission configuration indicator states without including the transmission configuration state that has been activated before that is deactivated.

11. The apparatus of any of claims 9 to 10, wherein the instructions, when executed by the at least one processor, cause the apparatus at least to: transmit, to a user equipment, a command to deactivate a transmission configuration indicator state before or after transmitting, to the network entity, the indication of the deactivation of the transmission configuration indicator state for the target cell; wherein the deactivation of the transmission configuration indicator state is performed with transmitting the command for an activation of transmission configuration indicator states without including a transmission configuration indicator state that has been activated before, wherein the transmission configuration indicator state that has been activated before is the transmission configuration indicator state that is deactivated; wherein the indication of the deactivation of the transmission configuration indicator state for the target cell transmitted to the network entity is based on the command transmitted to the user equipment for the activation of the transmission configuration indicator states without including the transmission configuration state that has been activated before that is deactivated.

12. The apparatus of any of claims 8 to 11, wherein the instructions, when executed by the at least one processor, cause the apparatus at least to: receive, from a user equipment, a layer 1 measurement report; wherein the determining to deactivate the transmission configuration indicator state for the target cell is based on the layer 1 measurement report received from the user equipment.

13. The apparatus of any of claims 1 to 12, wherein the instructions, when executed by the at least one processor, cause the apparatus at least to:transmit, from the apparatus to a source control unit control plane, an indication of the stopping of the data forwarding, wherein the apparatus comprises a source distributed unit.

14. The apparatus of any of claims 1 to 13, wherein the instructions, when executed by the at least one processor, cause the apparatus at least to: determine a timing advance validity expiration, a cell switch command, target cell measurements from a layer 1 report, or to trigger timing advance acquisition; and transmit, to the network entity, the indication to stop data forwarding, in response to determining the timing advance validity expiration, the cell switch command, the target cell measurements from a layer 1 report, or to trigger the timing advance acquisition.

15. The apparatus of any of claims 1 to 14, wherein the instructions, when executed by the at least one processor, cause the apparatus at least to: determine to trigger timing advance acquisition for a cell; and transmit, to a central unit, an indication that the timing advance acquisition for the cell is triggered; wherein the indication that the timing advance acquisition for the cell is triggered that is transmitted to the central unit comprises an indication to stop data forwarding to cells except for the cell for which the timing advance acquisition is triggered.

16. The apparatus of any of claims 1 to 15, wherein the instructions, when executed by the at least one processor, cause the apparatus at least to: determine to switch a user equipment from a source cell to a target cell; delay transmitting a cell switch command to the user equipment with an amount of time; start data forwarding towards a network entity that provides access to a targetcell with the amount of time before transmitting the cell switch command to the user equipment; and transmit the cell switch command to the user equipment with the amount of time after starting the data forwarding towards the network entity that provides access to the target cell.

17. The apparatus of any of claims 1 to 16, wherein the apparatus comprises a source distributed unit, and the network entity comprises a source control unit control plane.

18. The apparatus of any of claims 1 to 17, wherein the apparatus comprises the network entity.

19. An apparatus comprising: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus at least to: receive, from a network entity, one of: an indication to initiate data forwarding, or an indication to stop data forwarding; and perform one of: transmit a bearer context modification request in response to receiving from the network entity the indication to initiate data forwarding, or stop data forwarding in response to receiving from the network entity the indication to stop data forwarding.

20. The apparatus of claim 19, wherein the indication to initiate data forwarding is received based on a trigger other than a cell switch command.

21. The apparatus of any of claims 19 to 20, wherein the instructions, when executed by the at least one processor, cause the apparatus at least to: receive, from the network entity, the indication to initiate data forwarding, based on a determination to activate a transmission configuration indicator state.

22. The apparatus of any of claims 19 to 21, wherein the instructions, when executedby the at least one processor, cause the apparatus at least to: receive, from the network entity, the indication to initiate data forwarding, based on a determination to trigger early timing advance acquisition.

23. The apparatus of claim 22, wherein: a physical downlink control channel ordered random access channel is transmitted to a user equipment with a candidate identifier associated with a target cell; and the physical downlink control channel ordered random access channel transmitted to the user equipment with the candidate identifier associated with a target cell triggers the indication to initiate data forwarding.

24. The apparatus of any of claims 19 to 23, wherein the instructions, when executed by the at least one processor, cause the apparatus at least to: receive, from a user equipment, periodic layer 3 measurement reports; and trigger data forwarding from a control unit control plane, in response to receiving a layer 3 measurement report, and when a reference signal received power or reference signal received quality value of a serving cell or candidate cell is above or below a threshold.

25. The apparatus of any of claims 19 to 24, wherein the instructions, when executed by the at least one processor, cause the apparatus at least to: receive, from the network entity, the indication to stop data forwarding, based on a deactivation of a transmission configuration indicator state for a target cell.

26. The apparatus of claim 25, wherein the instructions, when executed by the at least one processor, cause the apparatus at least to: receive, from the network entity, an indication of the deactivation of the transmission configuration indicator state for the target cell; wherein the indication of the deactivation of the transmission configurationindicator state for the target cell received from the network entity comprises the indication to stop data forwarding.

27. The apparatus of claim 26, wherein the indication of the deactivation of the transmission configuration indicator state for the target cell received from the network entity is based on a medium access control control element comprising a command to deactivate the transmission configuration indicator state for the target cell.

28. The apparatus of any of claims 26 to 27, wherein the indication of the deactivation of the transmission configuration indicator state for the target cell received from the network entity is based on a command to deactivate a transmission configuration indicator state.

29. The apparatus of any of claims 25 to 28, wherein the deactivation of the transmission configuration indicator state for the target cell is based on a layer 1 measurement report of a user equipment.

30. The apparatus of any of claims 19 to 29, wherein the instructions, when executed by the at least one processor, cause the apparatus at least to: transmit, to a target control unit control plane, an indication of the stopping of the data forwarding.

31. The apparatus of any of claims 19 to 30, wherein the instructions, when executed by the at least one processor, cause the apparatus at least to: receive, from the network entity, the indication to stop data forwarding, based on a timing advance validity expiration, a cell switch command, or target cell measurements from a layer 1 report.

32. The apparatus of any of claims 19 to 31, wherein the instructions, when executed by the at least one processor, cause the apparatus at least to: determine to trigger timing advance acquisition for a cell; and receive, from a distributed unit, an indication that timing advance acquisition for a cell is triggered;wherein the indication that the timing advance acquisition for the cell is triggered that is received from the distributed unit comprises an indication to stop data forwarding to cells except for the cell for which the timing advance acquisition is triggered.

33. The apparatus of any of claims 19 to 32, wherein the instructions, when executed by the at least one processor, cause the apparatus at least to: determine to switch a user equipment from a source cell to a target cell; delay transmitting a cell switch command to the user equipment with an amount of time; initiate or start data forwarding towards a network entity that provides access to a target cell with the amount of time before transmitting the cell switch command to the user equipment; and transmit the cell switch command to the user equipment with the amount of time after starting the data forwarding towards the network entity that provides access to the target cell.

34. The apparatus of any of claims 19 to 33, wherein the apparatus comprises a source control unit control plane, and the network entity comprises a source distributed unit.

35. The apparatus of any of claims 19 to 34, wherein the apparatus comprises the network entity.

36. An apparatus comprising: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus at least to: receive, from a network entity, a handover request; and receive, from the network entity, an indication of a stopping of data forwarding;wherein the indication of the stopping of data forwarding is based on transmission configuration indicator state deactivation, a timing advance validity expiration, a cell switch command, target cell measurements from a layer 1 report, or a triggering of a timing advance acquisition.

37. The apparatus of claim 36, wherein the instructions, when executed by the at least one processor, cause the apparatus at least to: receive data forwarding from a source network entity with an amount of time before the source network entity transmits a cell switch command to a user equipment to switch to the apparatus, wherein the apparatus provides access to a target cell.

38. The apparatus of claim 37, wherein the network entity comprises the source control unit or the source distributed unit.

39. The apparatus of any of claims 36 to 38, wherein the network entity comprises a source control unit control plane.

40. The apparatus of any of claims 36 to 39, wherein the apparatus comprises a target control unit control plane.

41. The apparatus of any of claims 36 to 40, wherein the instructions, when executed by the at least one processor, cause the apparatus at least to: receive, from the network entity, an indication that the timing advance acquisition for a cell is triggered; wherein the indication that the timing advance acquisition for the cell is triggered that is received from the network entity comprises an indication to stop data forwarding to cells except for the cell for which the timing advance acquisition is triggered.

42. An apparatus comprising: at least one processor; and at least one memory storing instructions that, when executed by the at least oneprocessor, cause the apparatus at least to: transmit, to a network entity, a measurement report; wherein the measurement report is configured to be used with the network entity to determine whether to initiate data forwarding or stop data forwarding; and receive, from the network entity, an indication related to the determination of whether to initiate data forwarding or stop data forwarding.

43. The apparatus of claim 42, wherein the measurement report comprises a layer 1 measurement report and is configured to cause the network entity to activate a transmission configuration indicator state that triggers the initiation of data forwarding.

44. The apparatus of claim 43, wherein the instructions, when executed by the at least one processor, cause the apparatus at least to: receive, from the network entity, a medium access control control element comprising: a transmission configuration indicator state activation command, and a candidate identifier associated with a target cell; wherein the medium access control control element comprising the transmission configuration indicator state activation command and the candidate identifier associated with the target cell triggers the initiation of data forwarding; wherein the indication related to the determination of whether to initiate data forwarding or stop data forwarding comprises the medium access control control element comprising the transmission configuration indicator state activation command and the candidate identifier associated with the target cell.

45. The apparatus of any of claims 42 to 44, wherein the measurement report comprises a layer 1 measurement report and is configured to cause the network entity to trigger early timing advance acquisition that triggers the initiation of data forwarding.

46. The apparatus of claim 45, wherein the instructions, when executed by the at least one processor, cause the apparatus at least to:receive, from the network entity, a physical downlink control channel ordered random access channel with a candidate identifier associated with a target cell; wherein the physical downlink control channel ordered random access channel with the candidate identifier associated with the target cell triggers the initiating of data forwarding; wherein the indication related to the determination of whether to initiate data forwarding or stop data forwarding comprises the physical downlink control channel ordered random access channel with the candidate identifier associated with the target cell.

47. The apparatus of any of claims 42 to 46, wherein the instructions, when executed by the at least one processor, cause the apparatus at least to: transmit, to the network entity, periodic layer 3 measurement reports; and wherein the periodic layer 3 measurement reports are configured to cause the network entity to trigger data forwarding from a control unit control plane, when a reference signal received power or reference signal received quality value of a serving cell or candidate cell is above or below a threshold.

48. The apparatus of any of claims 42 to 47, wherein the instructions, when executed by the at least one processor, cause the apparatus at least to: receive, from the network entity, a medium access control control element comprising a command to deactivate a transmission configuration indicator state; wherein the command to deactivate the transmission configuration indicator state is based on receiving the medium access control control element for an activation of transmission configuration indicator states without including a transmission configuration indicator state that has been activated before, wherein the transmission configuration indicator state that has been activated before is the transmission configuration indicator state that is deactivated; wherein the medium access control control element comprising the commandto deactivate the transmission configuration indicator state triggers stopping of data forwarding; wherein the indication related to the determination of whether to initiate data forwarding or stop data forwarding received from the network entity comprises the medium access control control element comprising the command to deactivate the transmission configuration indicator state.

49. The apparatus of any of claims 42 to 48, wherein the instructions, when executed by the at least one processor, cause the apparatus at least to: receive, from the network entity, a command to deactivate a transmission configuration indicator state; wherein the command to deactivate the transmission configuration indicator state is based on receiving the command for an activation of transmission configuration indicator states without including a transmission configuration indicator state that has been activated before, wherein the transmission configuration indicator state that has been activated before is the transmission configuration indicator state that is deactivated; wherein the command to deactivate the transmission configuration indicator state triggers stopping of data forwarding; wherein the indication related to the determination of whether to initiate data forwarding or stop data forwarding received from the network entity comprises the command to deactivate the transmission configuration indicator state.

50. The apparatus of any of claims 42 to 49, wherein the measurement report comprises a layer 1 measurement report and is configured to cause the network entity to deactivate a transmission configuration indicator state for the target cell, wherein the deactivation of the transmission configuration indicator state for the target cell triggers stopping of data forwarding.

51. The apparatus of any of claims 42 to 50, wherein the apparatus comprises a user equipment, or a user equipment comprises the apparatus.

52. The apparatus of any of claims 42 to 51, wherein the instructions, when executed by the at least one processor, cause the apparatus at least to: receive, from a source network entity, a cell switch command to switch to a target network entity; wherein the cell switch command is received an amount of time after the source network entity starts data forwarding to the target network entity.

53. An apparatus comprising: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus at least to: receive, from a network entity, a bearer context modification request comprising an indication to initiate data forwarding; wherein the bearer context modification request comprising the indication to initiate data forwarding is based on one of: transmission configuration indicator state activation, early timing advance acquisition, a physical downlink control channel ordered random access channel, or a layer 3 measurement report that indicates that a reference signal received power or reference signal received quality value of a serving cell or candidate cell is above or below a threshold; and initiate data forwarding, based on the bearer context modification request comprising the indication to initiate data forwarding received from the network entity.

54. The apparatus of claim 53, wherein the apparatus comprises a source central unit user plane, and the network entity comprises a source central unit control plane.

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