Synchronization based on low-level mobility management

Abstract

The present disclosure relates to a handover method in a wireless network. A user equipment (UE) may be connected to a first next generation node B (gNB) of a 5G new radio (NR) network. The UE may then receive a handover command from the first gNB via one of layer 1 signaling or layer 2 signaling, the handover command instructing the UE to perform a handover procedure to a second gNB. The UE may then perform the handover procedure with the second gNB so that the UE is connected to the second gNB. Accordingly, the first gNB may instruct the UE to perform a handover procedure based on a handover command transmitted from the first gNB via one of layer 1 signaling or layer 2 signaling, wherein the handover command includes an identifier of a transmission and configuration indication (TCI) state associated with the second gNB.

Description

Background Art

[0001] A user equipment (UE) may establish a connection with at least one of a plurality of different networks or network types. The UE may establish the connection by connecting to a base station (e.g., a large cell, a small cell, an access point, etc.) of the network. As the UE moves, the UE may have to switch from a first base station to a second base station to maintain the connection to the network. This switching from a first base station to a second base station is called a handover, for example, the first base station hands over the UE to the second base station.

[0002] In Releases 15 and 16 of the 3GPP standard, handover is controlled based on Radio Resource Control (RRC) signaling between the base station and the UE. Those skilled in the art will appreciate that the RRC protocol is an Internet Protocol (IP) level layer or Layer 3 protocol. Summary of the invention

[0003] Some exemplary embodiments relate to a user equipment (UE) having a transceiver and a baseband processor. The transceiver is configured to connect to a first next generation node B (gNB) of a 5G new radio (NR) network. The baseband processor is configured to receive a handover command from the first gNB via one of layer 1 signaling or layer 2 signaling, the handover command instructing the UE to perform a handover procedure to a second gNB, and to perform the handover procedure with the second gNB so that the UE is connected to the second gNB.

[0004] Other exemplary embodiments are directed to a computer-readable storage medium having a set of instructions that, when executed by a processor, cause the processor to perform operations including: receiving a handover command from a first next-generation Node B (gNB) of a 5G New Radio (NR) network via one of layer 1 signaling or layer 2 signaling; the handover instructing a user equipment (UE) to perform a handover procedure to handover to a second gNB; and performing the handover procedure with the second gNB.

[0005] Other exemplary embodiments relate to a first next generation node B (gNB) of a 5G new radio (NR) network having a transceiver and a baseband processor. The transceiver is configured to be connected to a user equipment (UE). The baseband processor is configured to instruct the UE to perform a handover procedure from the first gNB to a second gNB based on a handover command transmitted from the first gNB via one of layer 1 signaling or layer 2 signaling, wherein the handover command includes an identification of a transmission and configuration indication (TCI) state associated with the second gNB. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Figure 1 Exemplary network arrangements are shown according to various exemplary embodiments.

[0007] Figure 2 An exemplary UE according to various exemplary embodiments is shown.

[0008] Figure 3 A first exemplary signaling diagram of a lower layer handover command and synchronization procedure based on a random access channel (RACH) according to various exemplary embodiments is shown.

[0009] Figure 4 A second exemplary signaling diagram of a RACH-less based lower layer handover command and synchronization procedure according to various exemplary embodiments is shown.

[0010] Figure 5 A diagram illustrating a UE handover from a source next-generation Node B (gNB) to a target gNB according to various exemplary embodiments.

[0011] Figure 6 A block diagram illustrating the relationship between transmission and configuration indication (TCI) states, synchronization signal blocks (SSBs), and physical RACH (PRACH) resources for RACH based handover according to various exemplary embodiments.

[0012] Figure 7 A scheduling diagram for RACH-less handover according to various exemplary embodiments is shown. DETAILED DESCRIPTION

[0013] The exemplary embodiments may be further understood with reference to the following description and related drawings, wherein similar elements have the same reference numerals.The exemplary embodiments relate to handover of a UE from a first base station to a second base station using lower layer (eg, layer 1 and / or layer 2) signaling.

[0014] The exemplary embodiments are described with respect to UE. However, reference to UE is provided for illustration purposes only. The exemplary embodiments may be used with any electronic component that can establish a connection with a network and is configured with hardware, software and / or firmware for exchanging information and data with the network. Therefore, UE described herein is used to represent any electronic component.

[0015] The exemplary embodiments are also described with reference to 5G New Radio (NR) radio access technology (RAT). However, it should be understood that 5G NR is used for illustrative purposes and the exemplary embodiments may be applied to any network that exhibits the characteristics and functions of the 5G NR network described below.

[0016] The exemplary embodiment is directed to using lower layer (e.g., Layer 1 and / or Layer 2, "L1 / L2") signaling for the handover process. Using lower layers for handover can reduce the delay and signaling overhead associated with the handover process. Typically, the exemplary embodiment uses L1 / L2 signaling from the base station to start the handover process. The UE receives the corresponding signaling and then synchronizes to the target cell. The exemplary embodiment addresses the signaling details of the L1 / L2 signaling and the UE behavior of synchronizing to the target cell. The exemplary embodiment will be described in detail below.

[0017] Figure 1 An exemplary network arrangement 100 according to various exemplary embodiments is shown. The exemplary network arrangement 100 includes a UE 110. Those skilled in the art will appreciate that the UE 110 may be any type of electronic component configured to communicate via a network, such as a mobile phone, a tablet computer, a desktop computer, a smart phone, a phablet, an embedded device, a wearable device, an Internet of Things (IoT) device, etc. It should also be appreciated that an actual network arrangement may include any number of UEs used by any number of users. Therefore, for purposes of illustration, only an example with a single UE 110 is provided.

[0018] UE 110 may be configured to communicate with one or more networks. In the example of network arrangement 100, the networks with which UE 110 may wirelessly communicate are 5G New Radio (NR) radio access network (5G NR-RAN) 120, LTE radio access network (LTE-RAN) 122, and wireless local area network (WLAN) 124. However, it should be understood that UE 110 may also communicate with other types of networks, and UE 110 may also communicate with the network via a wired connection. Therefore, UE 110 may include a 5G NR chipset that communicates with 5G NR-RAN 120, an LTE chipset that communicates with LTE-RAN 122, and an ISM chipset that communicates with WLAN 124.

[0019] 5G NR-RAN 120 and LTE-RAN 122 may be part of cellular networks that may be deployed by cellular providers (e.g., Verizon, AT&T, Sprint, T-Mobile, etc.). These networks 120, 122 may include, for example, cells or base stations (NodeB, eNodeB, HeNB, eNBS, gNB, gNodeB, macrocell base stations, microcell base stations, small cell base stations, femtocell base stations, etc.) configured to send and receive traffic from UEs equipped with appropriate cellular chipsets. WLAN 124 may include any type of wireless local area network (WiFi, hotspot, IEEE 802.11x network, etc.).

[0020] UE 110 may be connected to 5G NR-RAN 120 via gNB 120A or gNB 120B. gNB 120A and 120B may be configured with the necessary hardware, software and / or firmware to perform massive multiple-input multiple-output (MIMO) functionality. Massive MIMO may refer to a base station configured to generate multiple beams for multiple UEs. As will be described in more detail below, an exemplary embodiment will provide a way to hand over UE 110 from gNB 120A to gNB 120B, and vice versa. Reference to two gNBs 120A, 120B is for illustrative purposes only. The exemplary embodiment may be applied to any appropriate number of gNBs. In addition, UE 110 may communicate with eNB 122A of LTE-RAN 122 or an access point of WLAN 124.

[0021] Those skilled in the art will appreciate that any relevant process may be performed for the UE 110 to connect to the 5G NR-RAN 120. For example, as described above, the 5G NR-RAN 120 may be associated with a particular cellular provider, where the UE 110 and / or its user has protocol and credential information (e.g., stored on a SIM card). Upon detecting the presence of the 5G NR-RAN 120, the UE 110 may transmit corresponding credential information in order to associate with the 5G NR-RAN 120. More specifically, the UE 110 may be associated with a particular base station (e.g., gNB 120A of the 5G NR-RAN 120).

[0022] In addition to the networks 120, 122, and 124, the network arrangement 100 includes a cellular core network 130, the Internet 140, an IP multimedia subsystem (IMS) 150, and a network service backbone 160. The cellular core network 130 can be viewed as an interconnected collection of components that manage the operation and traffic of the cellular network. The cellular core network 130 also manages the traffic flowing between the cellular network and the Internet 140. The IMS 150 can be generally described as an architecture for delivering multimedia services to the UE 110 using the IP protocol. The IMS 150 can communicate with the cellular core network 130 and the Internet 140 to provide multimedia services to the UE 110. The network service backbone 160 communicates directly or indirectly with the Internet 140 and the cellular core network 130. The network service backbone 160 can be generally described as a set of components (e.g., servers, network storage arrangements, etc.) that implement a set of services that can be used to extend the functionality of the UE 110 to communicate with various networks.

[0023] Figure 2 An exemplary UE 110 is shown according to various exemplary embodiments. Figure 1100 is used to describe the UE 110. The UE 110 may represent any electronic device and may include a processor 205, a memory arrangement 210, a display device 215, an input / output (I / O) device 220, a transceiver 225, and other components 230. The other components 230 may include, for example, an audio input device, an audio output device, a battery to provide a limited power source, a data acquisition device, a port for electrically connecting the UE 110 to other electronic devices, one or more antenna panels, etc.

[0024] Processor 205 may be configured to execute multiple engines of UE 110. For example, the engines may include handover engine 235. Handover engine 235 may be configured to manage the operation of UE 110 during a handover process from gNB 120A to gNB 120B. The specific operations will be described in more detail below.

[0025] The above-described engine as an application (e.g., program) executed by the processor 205 is merely exemplary. The functions associated with the engine may also be represented as an independently integrated component of the UE 110, or may be a modular component coupled to the UE 110, such as an integrated circuit with or without firmware. For example, an integrated circuit may include an input circuit for receiving a signal and a processing circuit for processing the signal and other information. The engine may also be embodied as an application or multiple separate applications. In addition, in some UEs, the functionality described for the processor 205 is shared between two or more processors such as a baseband processor and an application processor. The exemplary embodiments may be implemented in any of these or other configurations of the UE.

[0026] The memory arrangement 210 may be a hardware component configured to store data related to operations performed by the UE 110. The display device 215 may be a hardware component configured to display data to a user, and the I / O device 220 may be a hardware component that enables user input. The display device 215 and the I / O device 220 may be separate components or may be integrated together (such as a touch screen). The transceiver 225 may be a hardware component configured to establish a connection with the 5G NR-RAN 120, LTE-RAN 122, WLAN 124, etc. Thus, the transceiver 225 may operate on multiple different frequencies or channels (e.g., a continuous set of frequencies).

[0027] Figure 3 and Figure 4 The signaling associated with two examples of lower layer based handover commands and synchronization procedures will be described. Figure 3 and Figure 4Before describing the signaling of the UE 110, it should be noted that in this description, it will be considered that UE 110 is currently connected to gNB 120A and a handover procedure is being performed to hand over the UE to gNB 120B. Therefore, gNB 120A will be considered as the "source gNB" and gNB 120B will be considered as the "target gNB". It should be understood that this is for illustration purposes only, and any gNB can be a source gNB or a target gNB, and the operations described herein are performed for each of these components.

[0028] Figure 3 A first exemplary signaling diagram 300 of a lower layer based handover command and synchronization procedure according to various exemplary embodiments is shown. The signaling diagram 300 may be viewed as a handover based on a random access channel (RACH) procedure.

[0029] In 310, the source gNB 120A sends an L1 / L2 based handover command to the UE 110. The L1 / L2 based handover command will be described in more detail below. In 320, the UE 110 sends an acknowledgment of the L1 / L2 handover command to the source gNB 120A. Although not shown in the signaling diagram 300, the UE 110 may also send an acknowledgment of the L1 / L2 handover command to the target gNB 120B. In 330, the UE 110 and the target gNB 120B perform a RACH procedure to complete the handover from the source gNB 120A to the target gNB 120B. The details of the L1 / L2 based handover command and the RACH procedure will be described in more detail below.

[0030] Figure 4 A second exemplary signaling diagram 400 of a lower layer based handover command and synchronization procedure according to various exemplary embodiments is shown. The signaling diagram 400 may be viewed as a RACH-less based handover.

[0031] In 410, the source gNB 120A sends an L1 / L2 based handover command to the UE 110. In 420, the UE 110 sends an acknowledgment of the L1 / L2 handover command to the source gNB 120A. In 430, the UE 110 and the target gNB 120B exchange handover messages on the configured physical uplink shared channel (PUSCH) to complete the handover from the source gNB 120A to the target gNB 120B. The details of the L1 / L2 based handover command and PUSCH message transmission will be described in more detail below.

[0032] Figure 5A diagram of a UE 110 handing over from a source gNB 120A to a target gNB 120B according to various exemplary embodiments is shown. As described above, in 310 and 410, the source gNB 120A will send an L1 / L2 based handover command to the UE 110 to initiate the handover process. The following description will refer to Figure 5 An exemplary L1 / L2 based handover command is described.

[0033] The gNB to which the UE is currently connected (e.g., gNB 120A) can provide a downlink beam indication based on a transmission and configuration indication (TCI). TCI can be used to indicate a quasi-co-sited (QCL) source reference signal for a downlink channel (PDSCH, PDCCH). If the properties of the channel transmitting symbols on one antenna port can be inferred from the channel transmitting symbols on another antenna port, the two antenna ports are considered to be quasi-co-sited. UE 110 can be configured with multiple (S) TCI state sets. In each TCI state set, multiple (N) TCI states can be configured. Each TCI state set can correspond to a serving cell. For example, in Figure 5 In the example, TCI state x can be considered to correspond to the TCI state set for source gNB 120A, while TCI state y can correspond to the TCI state set for target gNB 120B. This correspondence can be based on the physical cell ID (PCI) configured for each TCI state set or each TCI state. This correspondence allows implicit association, for example, gNBs can configure different PCIs in different TCI states, and TCI states sharing the same PCI can be considered to belong to the same set.

[0034] The L1 / L2 based handover command may be based on a TCI update command sent from the source gNB 120A to the UE 110. For example, as described in the above example, the source gNB 120A is associated with TCI state x, and the target gNB 120B is associated with TCI state y. Therefore, in the L1 / L2 based handover command, the source gNB 120A may send a TCI update command indicating TCI state y. Since the UE 110 is configured with information indicating that TCI state y is associated with the target gNB 120B, the UE 110 will understand that the source gNB 120A is signaling that a handover operation should be performed to hand over to the target gNB 120B.

[0035] The L1 / L2 based handover command (e.g., a TCI update command including a TCI state indication) may be included in a medium access control (MAC) control element (CE) (e.g., a layer 2 message), or in a downlink control information (DCI) message (e.g., a layer 1 message). The UE 110 may store various RRC parameter sets associated with different TCI state sets, which may then be used for handover. An example of this stored information is provided below. An exemplary L1 / L2 based handover command may be used in operation 310 or 410 for RACH based handover or RACH-free based handover.

[0036] The following is provided for reference as above Figure 3 Additional information for the RACH-based handover process described. For example, since the RACH process is being used and the candidate beams for the target cell 120B have been identified, such as TCI state y, the source gNB 120A may also provide physical RACH (PRACH) resources to the UE 110 to reduce additional delays for beam measurements. The PRACH resources may indicate the preamble index and time / frequency resources for the PRACH transmission. The UE 110 may derive the path loss for PRACH power control based on the synchronization signal block (SSB) / channel state indication-reference signal (CSI-RS) configured in the TCI state.

[0037] In a first exemplary embodiment, for each TCI state, the source gNB 120A may configure PRACH resources from the target cell 120B via RRC signaling. The RRC signaling described in this example is RRC signaling that occurs before the handover process begins, for example, during the normal process of RRC signaling that occurs when the UE 110 is connected to the gNB 120A. As described above, the UE 110 may store various RRC parameter sets associated with different TCI state sets. For example, as part of the TCI state information signaled to the UE 110, the source GNB 120A may include an indication of the PRACH resources for the TCI state. When the UE 110 receives an L1 / L2-based handover command that includes the TCI state, the UE 110 may retrieve information associated with the TCI state that includes the PRACH resources.

[0038] UE 110 may then start a RACH procedure based on the configured PRACH resources (e.g., Figure 3Operation 330). The initial attempt of the RACH procedure 330 may be a contention-free based RACH procedure. The UE 110 may monitor for a response after transmitting the PRACH, and if after a given time window, the UE 110 does not receive any response, the UE may fall back to using a contention-based RACH procedure. Completion of the RACH procedure 330 completes the handover from the source gNB 120A to the target gNB 120B.

[0039] Figure 6 A block diagram 600 is shown of the relationship between TCI states 610, SSBs 620 and 625, and PRACH resources 630 for RACH based handover according to various exemplary embodiments. In a second exemplary embodiment of RACH based handover, in each TCI state, the source gNB 120A can configure an SSB or a CSI-RS that is quasi-co-located with an SSB. In this example, TCI state 1 610 can be considered to be associated with the target gNB 120B. SSB 620 is associated with TCI 1 state 610 and PRACH resources 631-634. The association between PRACH resources 631-634 and SSB 620 from the target cell 120B can again be configured by RRC signaling in a manner similar to that described above with reference to TCI state information.

[0040] In this exemplary embodiment, UE 110 may randomly select one of the associated PRACH resources (e.g., PRACH resource 632) based on SSB 620 associated with TCI 1 state 610 of target gNB 120B, and perform a contention-based RACH procedure in 330. For example, in some embodiments, a radio network temporary ID (RNTI) of UE 110 in the target cell may be configured for each TCI state. UE 110 may transmit Msg3 including the RNTI to target gNB 120B. In other embodiments, target gNB 120B may not provide a new RNTI to UE 110. In this case, UE 110 may transmit Msg3 with an initial UE-ID for contention handling.

[0041] The following is provided for reference as above Figure 4 Additional information for the RACH-free handover process. Figure 7 A scheduling diagram 700 for RACH-free handover according to various exemplary embodiments is shown. The operations described with reference to the scheduling diagram 700 are related to the operations described above with reference to Figure 4 The PUSCH signaling 430.

[0042] At 710, UE 110 sends a PUSCH message to the target gNB 120B. The PUSCH resources used by UE 110 to communicate with the target gNB 120B can be configured in various ways. In some exemplary embodiments, PUSCH resources can be configured for each TCI state. Similarly, this information can be stored by UE 110 based on RRC signaling from source gNB 120A. The PUSCH configuration may include modulation and coding scheme (MCS), allocated bandwidth, time resources, DMRS port index, power control parameters, etc. UE 110 can transmit PUSCH using the same beam as the SSB / CSI-RS configured in the TCI state. In addition, UE 110 can derive path loss for PUSCH power control based on the SSB / CSI-RS configured in the TCI state.

[0043] In other exemplary embodiments, the PUSCH resources may be triggered by a PDCCH or MAC CE from the source gNB 120A. In one example, an indicator in the DCI may indicate whether the PDCCH triggers the PUSCH towards the source gNB 120A or towards the target gNB 120B. In another example, the PUSCH resources may be indicated by an L1 / L2 handover command from the source gNB 120A.

[0044] The initial scrambler for the PUSCH at 710 may be determined based on any one of the configured RNTI from the source gNB 120A, the index of the random access preamble, or the virtual cell ID of the target gNB 120B.

[0045] The UE 110 may also derive a timing advance (TA) for the PUSCH transmission 710. Various options may exist for deriving the TA. In a first example, the TA may be assumed to be 0. In a second example, the TA may be configured by the source gNB 120A. For example, the TA may be configured per TCI state set or TCI state.

[0046] In a third example, the TA may be based on measurements of the CSI-RS configured in the TCI state. In order to improve the TA measurement accuracy, the CSI-RS may be configured based on one or more of the following rules. The CSI-RS may be 1-port. The frequency density of the CSI-RS may be at least x resource elements / resource blocks (RE / RB), for example, x=3. The minimum bandwidth of the CSI-RS may be min{N_RB_max,N1}, where N_RB_max indicates the maximum number of RBs of the bandwidth portion, and N1 is a predetermined value, for example, N1=52, or based on the capabilities of the UE.

[0047] At 720, the target gNB 120B responds to the PUSCH message from the UE 110. The target gNB 120B response may be based on the PDCCH. As part of the response in 720, the target gNB 120B may schedule uplink (UL) transmissions with a scheduling offset K. The scheduling offset K may be determined as K2+δ, where K2 is the minimum scheduling offset and δ is an additional scheduling offset that is predefined based on the subcarrier spacing of the PUSCH.

[0048] At 730, UE 110 may then perform an UL transmission to target gNB 120B. Once this is completed, the handover process is complete and UE 110 is connected to target gNB 120B.

[0049] Those skilled in the art will appreciate that the exemplary embodiments described above may be implemented with any suitable software configuration or hardware configuration or combination thereof. Exemplary hardware platforms for implementing the exemplary embodiments may include, for example, Intel x86-based platforms with compatible operating systems, Windows OS, Mac platforms and MAC OS, mobile devices with operating systems such as iOS, Android, etc. In other examples, the exemplary embodiments of the above methods may be embodied as a program including lines of code stored on a non-transitory computer-readable storage medium, which, when compiled, may be executed on a processor or microprocessor.

[0050] Although this patent application describes various combinations of various embodiments each having different features, those skilled in the art will understand that any feature of an embodiment may be combined with features of other embodiments in any manner not publicly denied or with features that are not functionally or logically inconsistent with the operation or function of the device of the embodiments disclosed in the present invention.

[0051] It is understood that the use of personally identifiable information should be subject to privacy policies and practices that are generally recognized to meet or exceed industry or government requirements for maintaining user privacy. Specifically, personally identifiable information data should be managed and processed to minimize the risk of unintentional or unauthorized access or use, and the nature of the authorized use should be clearly stated to users.

[0052] It will be apparent to those skilled in the art that various modifications may be made to the present disclosure without departing from the spirit or scope of the present disclosure. Therefore, the present disclosure is intended to cover modifications and variations of the present disclosure, provided that these modifications and variations are within the scope of the appended claims and their equivalents.

Claims

1. A user equipment UE, comprising: A transceiver configured to connect to a first next generation Node B, i.e., a first gNB, of a 5G New Radio (NR) network; as well as A baseband processor, the baseband processor being configured to: receiving a handover command from the first gNB via one of layer 1 signaling or layer 2 signaling, the handover command instructing the UE to perform a handover procedure to a second gNB, wherein the handover command includes a transmission associated with the second gNB and an identifier of a configuration indicating a TCI state, and performing the handover procedure with the second gNB so that the UE is connected to the second gNB, The UE is configured to store a relationship between the second gNB and the identified TCI state, and also store a relationship between the identified TCI state and parameters for performing the handover procedure.

2. The UE of claim 1, wherein the layer 1 signaling or the layer 2 signaling comprises one of a medium access control (MAC) control element (CE) or a downlink control information (DCI) message.

3. The UE according to claim 1, further comprising: A memory configured to store a relationship between the second gNB and the identified TCI state, and also to store a relationship between the identified TCI state and parameters for performing the handover process.

4. The UE according to claim 1, wherein the handover process includes performing a random access channel (RACH) process between the UE and the second gNB.

5. The UE according to claim 4, wherein before receiving the handover command, the first gNB notifies the UE of the physical RACH resources, i.e., PRACH resources, on which the RACH process is to be performed.

6. The UE of claim 5, wherein a contention-free RACH procedure is attempted on the identified PRACH resources.

7. The UE of claim 4, wherein the handover command includes a transmission associated with the second gNB and an identifier of a configuration indicating a TCI state, and wherein the UE includes a synchronization signal block (SSB) and a PRACH resource corresponding to the identified TCI state, wherein the baseband processor performs a contention-based RACH procedure on one of the PRACH resources corresponding to the identified TCI state.

8. The UE of claim 1, wherein the handover process comprises performing Physical Uplink Shared Channel (PUSCH) message transmission between the UE and the second gNB.

9. The UE of claim 8, wherein the PUSCH resource used to perform the PUSCH message transmission is one of: (i) related to a transmission and configuration indication TCI state indicated in the handover command, or (ii) signaled to the UE from the first gNB.

10. The UE according to claim 8, wherein the baseband processor is configured to determine a timing advance TA of PUSCH resources.

11. The UE of claim 10, wherein the TA is determined based on at least one of: (i) a predetermined value, (ii) information received from the first gNB, or (iii) measurement of a channel state indication-reference signal (CSI-RS).

12. A computer-readable storage medium comprising a set of instructions that, when executed by a processor, cause the processor to perform operations comprising: receiving a handover command from a first next generation Node B, i.e., a first gNB, of a 5G New Radio (NR) network via one of layer 1 signaling or layer 2 signaling, the handover instructing a user equipment UE to perform a handover procedure to hand over to a second gNB, wherein the handover command includes a transmission associated with the second gNB and an identifier of a configuration indicating a TCI state; storing a relationship between the second gNB and the identified TCI state; storing a relationship between the identified TCI state and parameters for performing the handover process; as well as Perform the handover process with the second gNB.

13. The computer-readable storage medium of claim 12, wherein the handover process comprises performing a random access channel (RACH) process between the UE and the second gNB.

14. The computer-readable storage medium of claim 13, wherein the operations further comprise: Prior to receiving the handover command, receiving from the first gNB an indication of a physical RACH resource, i.e., a PRACH resource, on which the RACH procedure is to be performed; as well as A contention-free RACH procedure with the second gNB is attempted on the identified PRACH resources.

15. The computer-readable storage medium of claim 12, wherein the handover process comprises performing a physical uplink shared channel (PUSCH) message transmission between the UE and the second gNB, wherein a PUSCH resource used to perform the PUSCH message transmission is one of: (i) related to a transmission and configuration indication (TCI) state indicated in the handover command, or (ii) signaled from the first gNB to the UE.

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