Enhanced RACH-less handover with CBRA request based early ta acquisition

Abstract

A method includes: receiving, by a first user equipment (UE) from a source network node, a broadcast signal including an early timing advance (eTA) configuration for a neighboring cell; measuring, by the first UE, a reference signal received power (RSRP) of a reference signal of the neighboring cell; and transmitting, by the first UE to the target network node, a CBRA based RACH request for eTA acquisition prior to the target network node starting an eTA requirement report timer. The eTA configuration includes an indication of an eTA threshold, a contention- based random access (CBRA) resource associated with the neighboring cell, a preamble, a priority of a target network node, and a number of nodes to perform eTA. The target network node is configured to expect the UEs to report measurement results with PRACH information used to send eTA RACH requirements prior to an expiry of the eTA requirement report timer.

Description

ENHANCED RACH-LESS HANDOVER WITH CBRA REQUEST BASED EARLY TA ACQUISITIONFIELD

[0001] Various example embodiments relate generally to wireless networking and, more particularly, to configurations for enhanced RACH-less handover.BACKGROUND

[0002] Wireless networking provides significant advantages for user mobility. A user’s ability to remain connected while on the move provides advantages not only for the user, but also provides greater efficiency and productivity for society as a whole. As user expectations for connection reliability, data speed, and device battery life become more demanding, technology for wireless networking must also keep pace with such expectations. Accordingly, there is continuing interest in improving wireless networking technology.SUMMARY

[0003] According to some aspects, there is provided the subject matter of the independent claims. Some further aspects are defined in the dependent claims.

[0004] In accordance with aspects of the disclosure, a method includes: receiving, by a user equipment (UE) from a source network node providing a source cell, a broadcast signal including an early timing advance (eTA) configuration for a neighboring cell; measuring, by the UE, a reference signal received power (RSRP) of a reference signal of the neighboring cell, a priority of the neighboring cell, and / or a number of the neighboring cell to perform eTA; and transmitting a random access request towards the neighboring cell using the CBRA resource, in response to determining the measured RSRP being above the eTA threshold. The eTA configuration includes an indication of an eTA threshold and a contention-based random access (CBRA) resource associated with the neighboring cell. The CBRA resource includes PRACH information including a preamble, a RACH occasion, and / or a RACH frame timing.

[0005] In an aspect of the method, the eTA configuration may be a cell-specific configuration and includes a cell-specific eTA configuration for the neighboring cell and a separate cell-specificeTA configuration for a further neighboring cell. The indicated eTA threshold and / or the CBRA resource may be different from cell to cell.

[0006] In an aspect of the method, the method may further include transmitting, from the UE to the source network node, a message including a measurement report related to the neighboring cell, and an indication that an eTA request has been sent to the neighboring cell.

[0007] In an aspect of the method, the measuring by the UE may be performed after an eTA requirement report timer is started by the UE.

[0008] In an aspect of the method, the method may further include transmitting, by the UE, a CBRA based early timing advance (TA) request to the neighboring cell.

[0009] In an aspect of the method, the method may further include: receiving, by the UE from the source network node, a command to access the neighboring cell and an associated neighboring cell timing advance (TA) value; and performing a RACH-less access to the neighboring cell based on the received TA value.

[0010] In an aspect of the method, the method may further include: using, by the UE, CBRA RACH configuration information; and transmitting, by the UE, an early TA request to the neighboring cell.

[0011] In an aspect of the method, when the UE is measuring the neighboring cell, a target cell, and / or a target network node, the UE may be already in sync with the neighboring cell, the target cell, and / or the target network node.

[0012] In an aspect of the method, the UE may be able to utilize an in-sync state to send an early TA request to the neighboring cell.

[0013] In an aspect of the method, the method may further include: transmitting, by the UE to the source network node, PRACH information with a measurement report for the neighboring cell. The source network node may be configured to perform an enhanced handover decision based on the UE transmission. The source network node may prioritize the neighboring cell, a target cell, and / or a target network node for handover preparations, based on the UE transmission.

[0014] In accordance with aspects of the disclosure, a user equipment (UE) includes at least one processor and at least one memory storing instructions which, when executed by the at least one processor, cause the UE at least to perform a method as in any one of the foregoing methods.

[0015] In accordance with aspects of the disclosure, a processor-readable medium stores instructions which, when executed by at least one processor of a UE, cause the UE at least to perform a method as in any one of the foregoing methods.

[0016] In accordance with aspects of the disclosure, a method includes transmitting, by a source network node providing a source cell to a user equipment (UE), a broadcast signal including an early timing advance (eTA) configuration for a neighboring cell; and receiving, by the source network node, a random access request towards the neighboring cell using the CBRA resource, in response to determining a measured reference signal received power (RSRP) being above the eTA threshold. The eTA configuration includes an indication of an eTA threshold and a contentionbased random access (CBRA) resource associated with the neighboring cell. The CBRA resource includes PRACH information including a preamble, a RACH occasion, and / or a RACH frame timing.

[0017] In an aspect of the method, the method may further include starting, by the source network node, an eTA requirement report timer. The source network node may be configured to expect the UE to report measurement results with the PRACH information used to send eTA RACH requirements prior to an expiry of the eTA requirement report timer.

[0018] In an aspect of the method, the method may further include receiving, by the source network node from the UE, a message indicating that an eTA request has been sent to the neighboring cell. The message may be included in the next measurement report to reduce signaling.

[0019] In an aspect of the method, the method may further include performing, by the source network node, an enhanced handover decision, the source network node prioritizing the neighboring cell, a target cell, and / or a target network node for handover preparations based on the UE reporting the PRACH information with a measurement report for the neighboring cell over another candidate cell for which the UE has not performed eTA, considering all other handover criteria are met.

[0020] In an aspect of the method, the CBRA resource may include a cell-specific eTA threshold configured to enable the UE to evaluate the neighboring cell without any explicit signaling between the source network node and the UE.

[0021] In an aspect of the method, the method may further include receiving, by the source network node from the UE, measurement results including PRACH information based on expiration of the eTA requirement report timer.

[0022] In an aspect of the method, the method may further include transmitting, by the source network node to the neighboring cell, a handover preparation request including PRACH information and legacy content, for handover preparation.

[0023] In accordance with aspects of the disclosure, a network apparatus includes at least one processor and at least one memory storing instructions which, when executed by the at least one processor, cause the network apparatus at least to perform a method as in any one of the foregoing methods.

[0024] In accordance with aspects of the disclosure, a processor-readable medium stores instructions which, when executed by at least one processor of a network apparatus, cause the network apparatus at least to perform a method as in any one of the foregoing methods.

[0025] In accordance with aspects of the disclosure, a method includes receiving, by a user equipment (UE) from a source network node providing a source cell, a radio resource control (RRC) message including a first early timing advance (eTA) configuration for a neighboring cell and a measurement configuration for a neighboring cell; measuring, by the UE, a reference signal received power (RSRP) of a reference signal of the neighboring cell, a priority of the neighboring cell, and / or a number of the neighboring cell; and transmitting a random access request towards the neighboring cell using the CBRA resource of the first eTA configuration, in response to determining the measured RSRP being above the eTA threshold of the first eTA configuration. The first eTA configuration includes an indication of an eTA threshold and a contention-based random access (CBRA) resource associated with the neighboring cell. The CBRA resource includes PRACH information including a preamble, a RACH occasion, and / or a RACH frame timing.

[0026] In an aspect of the method, the first eTA configuration may be a UE-specific configuration. A speed, class, location, and / or measurement reporting offset may be different from UE to UE.

[0027] In an aspect of the method, the method may further include receiving, by the UE from the source network node providing the source cell, a broadcast signal including a second eTA configuration for the neighboring cell.

[0028] In an aspect of the method, the second eTA configuration may be a cell-specific configuration and include a cell-specific eTA configuration for the neighboring cell and a separate cell-specific eTA configuration for a further neighboring cell. The indicated eTA threshold and / or the CBRA resource may be different from cell to cell.

[0029] In an aspect of the method, the method may further include transmitting, from the UE to the source network node, a message including a measurement report related to the neighboring cell, and an indication that an eTA request has been sent to the neighboring cell.

[0030] In an aspect of the method, the method may further include transmitting, by the UE, a CBRA based eTA request to the neighboring cell.

[0031] In an aspect of the method, the UE may be receiving from the source network node a command to access the neighboring cell and an associated neighboring cell timing advance (TA) value, and performing a RACH-less access to the neighboring cell based on the received TA value.

[0032] In an aspect of the method, the method may further include: using, by the UE, CBRA RACH configuration information; and transmitting, by the UE an early TA request to the neighboring cell.

[0033] In an aspect of the method, when the UE is performing the measurement of the neighboring cell, target cell, and / or the target network node, and the UE may already be in sync with the neighboring cell, target cell, and / or target network node.

[0034] In an aspect of the method, the UE may utilize this in-sync state to send early TA request to the neighboring cell.

[0035] In accordance with aspects of the disclosure, a user equipment (UE) includes at least one processor and at least one memory storing instructions which, when executed by the at least one processor, causes the UE at least to perform a method as in any one of the foregoing methods.

[0036] In accordance with aspects of the disclosure, a processor-readable medium stores instructions which, when executed by at least one processor of a UE, cause the UE at least to perform a method as in any one of the foregoing methods.

[0037] In accordance with aspects of the disclosure, a method includes transmitting, by a source network node providing a source cell to a user equipment (UE), a radio resource control (RRC) message including a first early timing advance (eTA) configuration for a neighboring cell and a measurement configuration for a neighboring cell; and receiving, by the source network node, a random access request towards the neighboring cell using the CBRA resource, in responseto determining a measured reference signal received power (RSRP) being above the eTA threshold. The first eTA configuration includes an indication of an eTA threshold and a contentionbased random access (CBRA) resource associated with the neighboring cell. The CBRA resource includes PRACH information including a preamble, a RACH occasion, and / or a RACH frame timing;

[0038] In an aspect of the method, the first eTA configuration may be a UE-specific configuration. A speed, class, location, and / or measurement reporting offset may be different from UE to UE.

[0039] In an aspect of the method, the method may further include transmitting, by the source network node providing the source cell to the UE, a broadcast signal including a second eTA configuration for the neighboring cell.

[0040] In an aspect of the method, the second eTA configuration may be a cell-specific configuration and include a cell-specific eTA configuration for the neighboring cell and a separate cell-specific eTA configuration for a further neighboring cell. The indicated eTA threshold and / or the CBRA resource may be different from cell to cell.

[0041] In an aspect of the method, the method may further include receiving, by the source network node from the UE, a message indicating that an eTA request has been sent to the neighboring cell. The message may be included in the next measurement report to reduce signaling.

[0042] In an aspect of the method, the method may further include transmitting, by the source network node, a handover preparation request including PRACH information and legacy content, to the neighboring cell, for handover preparation.

[0043] In an aspect of the method, the method may further include : recognizing, by the source network node, an incoming handover preparation request; associating the UE with the PRACH information; and transmitting, by the source network node to the UE, a stored timing advance (TA) in a handover command message piggybacked in a handover request acknowledgement.

[0044] In accordance with aspects of the disclosure, a network apparatus includes at least one processor and at least one memory storing instructions which, when executed by the at least one processor, causes the network apparatus at least to perform a method as in any one of the foregoing methods.

[0045] In accordance with aspects of the disclosure, a processor-readable medium stores instructions which, when executed by at least one processor of a network apparatus, cause the network apparatus at least to perform a method as in any one of the foregoing methods.

[0046] In accordance with aspects of the disclosure, a method includes: transmitting, from a user equipment (UE) to a source network node providing a source cell, a message including a measurement report related to a neighboring cell; receiving, by the UE from the source network node providing the source cell, a physical downlink control channel (PDCCH) order to send an early timing advance (eTA) request to the neighboring cell; and transmitting, by the UE, a contention-based random access (CBRA) eTA request to the neighboring cell. The PDCCH order includes a priority of the neighboring cell and / or a number of the neighboring cell

[0047] In an aspect of the method, the method may further include receiving, by the UE from the source network node providing a source cell, a radio resource control (RRC) message including a first early timing advance (eTA) configuration and a measurement configuration for a neighboring cell. The first eTA configuration may include an indication of an eTA threshold and a contention-based random access (CBRA) resource associated with the neighboring cell, and the CBRA resource may include PRACH information including a preamble, a RACH occasion, and / or a RACH frame timing;

[0048] In an aspect of the method, the neighboring cell may recognize the CBRA eTA request based on the preamble of the PRACH information.

[0049] In an aspect of the method, the first eTA configuration may be a UE-specific configuration. A speed, class, location, and / or measurement reporting offset may be different from UE to UE.

[0050] In an aspect of the method, the method may further include receiving, by the UE from the source network node providing a source cell, a broadcast signal including a second eTA configuration for the neighboring cell.

[0051] In an aspect of the method, the second eTA configuration may be a cell-specific configuration and include a cell-specific eTA configuration for the neighboring cell and a separate cell-specific eTA configuration for a further neighboring cell. The indicated eTA threshold and / or the CBRA resource may be different from cell to cell.

[0052] In an aspect of the method, the method may further include transmitting, from the UE to the source network node, an indication that an eTA request has been sent to the neighboring cell.

[0053] In an aspect of the method, the UE may be receiving from the source network node a command to access the neighboring cell and an associated neighboring cell timing advance (TA) value, and performing a RACH-less access to the neighboring cell based on the received TA value.

[0054] In an aspect of the method, the method may further include: using, by the UE, CBRA RACH configuration information; and transmitting, by the UE an early TA request to the neighboring cell.

[0055] In an aspect of the method, when the UE is performing the measurement of the neighboring cell, target cell, and / or the target network node, and the UE may already be in sync with the neighboring cell, target cell, and / or target network node.

[0056] In accordance with aspects of the disclosure, a user equipment (UE) includes at least one processor and at least one memory storing instructions which, when executed by the at least one processor, cause the UE at least to perform a method as in any one of the foregoing methods.

[0057] In accordance with aspects of the disclosure, a processor-readable medium stores instructions which, when executed by at least one processor of a UE, cause the UE at least to perform a method as in any one of the foregoing methods.

[0058] In accordance with aspects of the disclosure, a method includes: receiving, by a source network node providing a source cell, a message including a measurement report related to a neighboring cell; determining, by the source network node providing the source cell, that a measured reference signal received power (RSRP) is above an eTA threshold based on the measurement report; and transmitting, by the source network node providing the source cell to a user equipment (UE), a physical downlink control channel (PDCCH) order to send an early timing advance (eTA) request to the neighboring cell. The PDCCH order includes a priority of the neighboring cell and / or a number of the neighboring cell.

[0059] In an aspect of the method, the method may further include transmitting, by the source network node providing the source cell to the UE, a radio resource control (RRC) message including a first eTA configuration and a measurement configuration for a neighboring cell. The first eTA configuration may include an indication of the eTA threshold and a contention-based random access (CBRA) resource associated with the neighboring cell. The CBRA resource mayinclude PRACH information including a preamble, a RACH occasion, and / or a RACH frame timing.

[0060] In an aspect of the method, the first eTA configuration may be a UE-specific configuration. A speed, class, location, and / or measurement reporting offset may be different from UE to UE.

[0061] In an aspect of the method, the method may further include transmitting, by the source network node providing the source cell to the UE, a broadcast signal including a second eTA configuration for the neighboring cell.

[0062] In an aspect of the method, the second eTA configuration may be a cell-specific configuration and include a cell-specific eTA configuration for the neighboring cell and a separate cell-specific eTA configuration for a further neighboring cell. The indicated eTA threshold and / or the CBRA resource may be different from cell to cell.

[0063] In an aspect of the method, the method may further include receiving, by the source network node from the UE, a message indicating that an eTA request has been sent to the neighboring cell. The message may be included in the next measurement report to reduce signaling.

[0064] In an aspect of the method, the method may further include transmitting, by the source network node, a handover preparation request including PRACH information and legacy content, to the neighboring cell, for handover preparation.

[0065] In an aspect of the method, the method may further include: recognizing, by the source network node, an incoming handover preparation request; associating the UE with the PRACH information; and transmitting, by the source network node to the UE, a stored timing advance (TA) in a handover command message piggybacked in a handover request acknowledgement.

[0066] In accordance with aspects of the disclosure, a network apparatus includes at least one processor and at least one memory storing instructions which, when executed by the at least one processor, causes the network apparatus at least to perform a method as in any one of the foregoing methods.

[0067] In accordance with aspects of the disclosure, a processor-readable medium stores instructions which, when executed by at least one processor of a UE, cause the UE at least to perform a method as in any one of the foregoing methods.

[0068] In accordance with aspects of the disclosure, a method includes receiving, by a first user equipment (UE) from a source network node providing a source cell, a broadcast signal including an early timing advance (eTA) configuration for a neighboring cell; measuring, by the first UE, a reference signal received power (RSRP) of a reference signal of the neighboring cell; and transmitting, by the first UE to the source network node, a measurement report including PRACH information. The eTA configuration includes an indication of an eTA threshold, a contention-based random access (CBRA) resource associated with the neighboring cell, a preamble, a priority of a target network node, and a number of nodes to perform eTA associated with the neighboring cell. The PRACH information includes a preamble, a RACH occasion, and a RACH frame timing. The PRACH information is the same as a second UE within a predetermined time period.

[0069] In an aspect of the method, the method may further include receiving, by the first UE from the source network node, a CBRA based PDCCH order to retry for eTA acquisition based on contention.

[0070] In an aspect of the method, the method may further include transmitting, from the first UE to the source network node, a message including a measurement report with PRACH info related to the neighboring cell, an indication that an eTA request has been sent to the neighboring cell, and the CBRA resource with the neighboring cell.

[0071] In an aspect of the method, the method may further include performing, by the first UE, a CFRA based eTA request with the neighboring cell.

[0072] In an aspect of the method, the method may further include receiving, by the first UE from the source network node, a handover command with timing advance. The handover command may include a message indicating to fallback to RACH based handover.

[0073] In an aspect of the method, the measuring by the UE may be performed after an eTA requirement report timer is started by the UE.

[0074] In an aspect of the method, the PDCCH order may be received by the first UE and the second UE in a time staggered manner.

[0075] In accordance with aspects of the disclosure, a user equipment (UE) includes at least one processor and at least one memory storing instructions which, when executed by the at least one processor, causes the UE at least to perform a method as in any one of the foregoing methods

[0076] In accordance with aspects of the disclosure, a processor-readable medium stores instructions which, when executed by at least one processor of a UE, cause the UE at least to perform a method as in any one of the foregoing methods.

[0077] In accordance with aspects of the disclosure, a method includes transmitting, by a source network node to a first user equipment (UE) and to a second UE, a broadcast signal including an early timing advance (eTA) configuration for a neighboring cell; and receiving, by the source network node, a measurement report including PRACH information. The eTA configuration includes an indication of an eTA threshold, a contention-based random access (CBRA) resource associated with the neighboring cell, a preamble, a priority of a target network node, and a number of nodes to perform eTA associated with the neighboring cell. The PRACH information includes a preamble, a RACH occasion, and a RACH frame timing. The PRACH information is the same as the second UE within a predetermined time period.

[0078] In an aspect of the method, the method may further include starting, by the source network node, an eTA requirement report timer. The source network node may be configured to expect the first UE and the second UE to report measurement results with PRACH information used to send eTA RACH requirements prior to an expiry of the eTA requirement report timer.

[0079] In an aspect of the method, the method may further include receiving, by the source network node from each of the first UE and the second UE, a message indicating that an eTA request has been sent to the neighboring cell with the same PRACH information within an eTA requirement reporting time period.

[0080] In an aspect of the method, the method may further include detecting, by the source network node, a contention for CBRA based eTA acquisition request within a period of the eTA requirement report timer.

[0081] In an aspect of the method, the method may further include transmitting, by the source network node to each of the first and second UE, a PDCCH order to retry for CBRA based or CFRA based eTA acquisition because of the detected contention.

[0082] In an aspect of the method, the source network node may further provide a RACH type to perform early timing advance acquisition. A criteria for providing the RACH type may include a speed of each of the first and second UE, a DI and U1 RF condition, and a service type to which each of the first and second UE is subscribed.

[0083] In an aspect of the method, the method may further include determining, by the source network node, a handover decision; and transmitting, by the source network node to each of the first and second UE, a PDCCH order with PRACH resource for CFRA based eTA for the neighbor cell.

[0084] In an aspect of the method, the method may further include transmitting, by the source network node, a handover preparation request for the first and second UE. The handover preparation request may include PRACH information and legacy content, to the neighboring cell, for handover preparation.

[0085] In an aspect of the method, the method may further include transmitting, by the source network node to the neighboring cell, PRACH information and a contention detected flag to target in a handover request message.

[0086] In an aspect of the method, the method may further include transmitting, by the source network node to the neighboring cell, a handover request message after an expiration of an eTA requirement report timer or after the measurement report is received and a handover decision is made.

[0087] In an aspect of the method, the method may further include transmitting, by the source network node to the neighboring cell, a handover request message with the PRACH information received in the measurement report.

[0088] In an aspect of the method, the method may further include transmitting, by the source network node to the neighboring cell, a handover request message and a contention detected flag, in a case where the source network node receives another measurement report with same PRACH information within a time period of the eTA request report.

[0089] In an aspect of the method, the method may further include transmitting, by the source network node, a handover preparation request for the first UE. The handover preparation request may include PRACH information and legacy content, to the neighboring cell, for handover preparation.

[0090] In accordance with aspects of the disclosure, a network apparatus includes at least one processor and at least one memory storing instructions which, when executed by the at least one processor, causes the network apparatus at least to perform a method as in any one of the foregoing methods.

[0091] In accordance with aspects of the disclosure, a processor-readable medium stores instructions which, when executed by at least one processor of a network apparatus, cause the network apparatus at least to perform a method as in any one of the foregoing methods.

[0092] In accordance with aspects of the disclosure, a method includes: receiving by a first user equipment (UE) from a source network node, a broadcast signal including an early timing advance (eTA) configuration for a neighboring cell; measuring, by the first UE, a reference signal received power (RSRP) of a reference signal of the neighboring cell; and transmitting, by the first UE to the target network node, a CBRA based RACH request for eTA acquisition prior to the target network node starting an eTA requirement report timer. The eTA configuration includes an indication of an eTA threshold, a contention-based random access (CBRA) resource associated with the neighboring cell, a preamble, a priority of a target network node, and a number of nodes to perform eTA. The target network node is configured to expect the first UE and a second UE to report measurement results with PRACH information used to send eTA RACH requirements prior to an expiry of the eTA requirement report timer.

[0093] In an aspect of the method, the method may further include determining, by the first UE, that a handover command is not received from the target network node within a time period.

[0094] In an aspect of the method, the determination may include determining that a retry value is less than an eTA RACH counter value.

[0095] In an aspect of the method, the method may further include transmitting, by the first UE to the target network node, a CBRA based RACH request to retry for eTA acquisition based on contention.

[0096] In an aspect of the method, the method may further include transmitting, from the UE to the source network node, a message including a measurement report with PRACH information related to the neighboring cell, an indication that an eTA request has been sent to the neighboring cell, and the CBRA resource with the neighboring cell.

[0097] In an aspect of the method, the method may further include receiving, by the first UE from the source network node, a handover command with timing advance. The handover command may include a message indicating to fallback to RACH based handover.

[0098] In an aspect of the method, the method may further include receiving, by the first UE from the source network node, an RRC reconfiguration indicating to fallback to CFRA based eTA acquisition.

[0099] In accordance with aspects of the disclosure, a user equipment (UE) includes at least one processor and at least one memory storing instructions which, when executed by the at least one processor, cause the UE at least to perform a method as in any one of the foregoing methods.

[0100] In accordance with aspects of the disclosure, a processor-readable medium storing instructions which, when executed by at least one processor of a UE, cause the UE at least to perform a method as in any one of the foregoing methods

[0101] In accordance with aspects of the disclosure, a method includes: receiving, by a target network node from a first UE, a CBRA based RACH request for eTA acquisition prior to the target network node starting an eTA requirement report timer; receiving, by the target network node for each of the first UE and a second UE, within a predetermined time period, a handover request message from a source network node including PRACH information, the PRACH information including a preamble, a RACH occasion, a RAC frame, and timing; and detecting, by the target network node, a contention caused by the first UE and the second UE. The target network node is configured to expect the first UE and a second UE to report, to a source network node serving a source cell, measurement results with PRACH information used to send eTA RACH requirements prior to an expiry of the eTA requirement report timer to enable the source network node to send a handover request to the target network node. The PRACH information from the first UE is the same as the PRACH information from the second UE

[0102] In an aspect of the method, the method may further include starting, by the target network node, an eTA requirement report timer.

[0103] In an aspect of the method, the method may further include receiving, by the target network node from the second UE, a CBRA based RACH request for eTA acquisition after the target network node starts the eTA requirement report timer.

[0104] In an aspect of the method, the method may further include receiving, by the target network node from the first UE, a CBRA based RACH request to retry for eTA acquisition based on the contention.

[0105] In an aspect of the method, the method may further include transmitting, by the target network node to a source network node, a handover request message including a message indicating to fallback to RACH based handover.

[0106] In an aspect of the method, the method may further include transmitting, by the target network node to a source network node, an RRC reconfiguration indicating to fallback to CFRA based eTA acquisition.

[0107] In an aspect of the method, the method may further include transmitting, by the target network node to a source network node, a handover request message including PRACH information and legacy content for handover preparation.

[0108] In an aspect of the method, the method may further include receiving, by the target network node from the first UE, a timing advance preamble to trigger eTA acquisition.

[0109] In an aspect of the method, the method may further include transmitting, by the target network node to a source network node, an RRC configuration message for the first UE and the second UE for RRC reconfiguration preparation.

[0110] In accordance with aspects of the disclosure, a network apparatus includes at least one processor and at least one memory storing instructions which, when executed by the at least one processor, causes the network apparatus at least to perform a method as in any one of the foregoing methods.

[0111] In accordance with aspects of the disclosure, a processor-readable medium stores instructions which, when executed by at least one processor of a network apparatus, cause the network apparatus at least to perform a method as in any one of the foregoing methods.BRIEF DESCRIPTION OF THE DRAWINGS

[0112] Some example embodiments will now be described with reference to the accompanying drawings.

[0113] FIG. 1 is a diagram of an example embodiment of wireless networking between a network system and a user equipment (UE), according to one illustrated aspect of the disclosure;

[0114] FIG. 2 is a diagram of example components of a network system, according to one illustrated aspect of the disclosure;

[0115] FIG. 3 is a diagram illustrating preamble management, according to one illustrated aspect of the disclosure;

[0116] FIGS. 4 A and 4B are diagram of an example embodiment of signals and operations among a UE, a source wireless station or source node (e.g., network node (such as gNodeB(gNB))), according to one illustrated aspect of the disclosure, and a target node (e.g., network node (such as gNodeB (gNB))), according to one illustrated aspect of the disclosure;

[0117] FIGS. 5A and 5B are a diagram of an example embodiment of signals and operations among a UE, a source wireless station or source node (e.g., network node (such as gNodeB (gNB))), according to one illustrated aspect of the disclosure, and a target node (e.g., network node (such as gNodeB (gNB))), according to one illustrated aspect of the disclosure;

[0118] FIGS. 6A-6C are a diagram of an example embodiment of signals and operations among a UE, a source wireless station or source node (e.g., network node (such as gNodeB (gNB))), according to one illustrated aspect of the disclosure, and a target node (e.g., network node (such as gNodeB (gNB))), according to one illustrated aspect of the disclosure;

[0119] FIGS. 7A-7F are a diagram of an example embodiment of signals and operations among a UE, a source wireless station or source node (e.g., network node (such as gNodeB (gNB))), according to one illustrated aspect of the disclosure, and a target node (e.g., network node (such as gNodeB (gNB))), according to one illustrated aspect of the disclosure; and

[0120] FIG. 8 is a diagram of an example block diagram of a wireless station or node (e.g., network node (such as gNodeB (gNB)), user node or UE, relay node, or other node), according to one illustrated aspect of the disclosure.DETAILED DESCRIPTION

[0121] In the following description, certain specific details are set forth in order to provide a thorough understanding of the disclosed aspects. However, one skilled in the relevant art will recognize that aspects may be practiced without one or more of these specific details or with other methods, components, materials, etc. In other instances, well-known structures associated with transmitters, receivers, or transceivers have not been shown or described in detail to avoid unnecessarily obscuring descriptions of the aspects.

[0122] Reference throughout this specification to “one aspect” or “an aspect” means that a particular feature, structure, or characteristic described in connection with the aspect is included in at least one aspect. Thus, the appearances of the phrases “in one aspect” or “in an aspect” in various places throughout this specification are not necessarily all referring to the same aspect. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more aspects.

[0123] Embodiments described in the present disclosure may be implemented in wireless networking apparatuses, such as, without limitation, apparatuses utilizing Worldwide Interoperability for Microwave Access (WiMAX), Global System for Mobile communications (GSM, 2G), GSM EDGE radio access Network (GERAN), General Packet Radio Service (GRPS), Universal Mobile Telecommunication System (UMTS, 3G) based on basic wideband-code division multiple access (W-CDMA), high-speed packet access (HSPA), Long Term Evolution (LTE), LIE- Advanced, enhanced LTE (eLTE), 5G New Radio (5G NR), 5G Advance, 6G (and beyond) and 802.1 lax (Wi-Fi 6), among other wireless networking systems. The term ‘eLTE’ here denotes the LTE evolution that connects to a 5G core. LTE is also known as evolved UMTS terrestrial radio access (EUTRA) or as evolved UMTS terrestrial radio access network (EUTRAN).

[0124] The present disclosure may use the term “serving network device” to refer to a network node or network device (or a portion thereof) that services a UE. As used herein, the terms “transmit to,” “receive from,” and “cooperate with,” (and their variations) include communications that may or may not involve communications through one or more intermediate devices or nodes. The term “acquire” (and its variations) includes acquiring in the first instance or reacquiring after the first instance. The term “connection” may mean a physical connection or a logical connection.

[0125] The present disclosure uses 5G NR as an example of a wireless network and may use smartphones and / or extended reality headsets as an example of user equipments (UEs). It is intended and shall be understood that such examples are merely illustrative, and the present disclosure is applicable to other wireless networks and user equipment.

[0126] FIG. 1 is a diagram depicting an example of wireless networking between a network system 100 and a user equipment (UE) 150. The network system 100 may include one or more network nodes 120, one or more servers 110, and / or one or more network equipment 130 (e.g., test equipment). The network nodes 120 will be described in more detail below. As used herein, the term “network apparatus” may refer to any component of the network system 100, such as the server 110, the network node 120, the network equipment 130, any component(s) of the foregoing, and / or any other component(s) of the network system 100. Examples of network apparatuses include, without limitation, apparatuses implementing aspects of 5G NR, among others. The present disclosure describes embodiments related to 5GNR and embodiments that involve aspects defined by 3rd Generation Partnership Project (3GPP). However, it is contemplated thatembodiments relating to other wireless networking technologies are encompassed within the scope of the present disclosure.

[0127] The following description provides further details of examples of network nodes. In a 5G NR network, a gNodeB (also known as gNB) may include, e.g., a node that provides new radio (NR) user plane and control plane protocol terminations towards the UE and that is connected via a NG interface to the 5G core (5GC), e.g., according to 3GPP TS 38.300 V16.6.0 (2021-06) section 3.2, which is hereby incorporated by reference herein.

[0128] A gNB supports various protocol layers, e.g., Layer 1 (LI) - physical layer, Layer 2 (L2), and Layer 3 (L3).

[0129] The layer 2 (L2) of NR is split into the following sublayers: Media Access Control (MAC), Radio Link Control (RLC), Packet Data Convergence Protocol (PDCP) and Service Data Adaptation Protocol (SDAP), where, e.g.:o The physical layer offers to the MAC sublayer transport channels;o The MAC sublayer offers to the RLC sublayer logical channels;o The RLC sublayer offers to the PDCP sublayer RLC channels;o The PDCP sublayer offers to the SDAP sublayer radio bearers;o The SDAP sublayer offers to 5GC quality of service (QoS) flows;o Control channels include broadcast control channel (BCCH) and physical control channel (PCCH).

[0130] Layer 3 (L3) includes, e.g., radio resource control (RRC), e.g., according to 3GPP TS 38.300 V16.6.0 (2021-06) section 6, which is hereby incorporated by reference herein.

[0131] A gNB central unit (gNB-CU) includes, e.g., a logical node hosting, e.g., radio resource control (RRC), service data adaptation protocol (SDAP), and packet data convergence protocol (PDCP) protocols of the gNB or RRC and PDCP protocols of the en-gNB, that controls the operation of one or more gNB distributed units (gNB-DUs). The gNB-CU terminates the Fl interface connected with the gNB-DU. A gNB-CU may also be referred to herein as a CU, a central unit, a centralized unit, or a control unit.

[0132] A gNB Distributed Unit (gNB-DU) includes, e.g., a logical node hosting, e.g., radio link control (RLC), media access control (MAC), and physical (PHY) layers of the gNB or en-gNB, and its operation is partly controlled by the gNB-CU. One gNB-DU supports one or multiple cells. One cell is supported by only one gNB-DU. The gNB-DU terminates the Fl interfaceconnected with the gNB-CU. A gNB-DU may also be referred to herein as DU or a distributed unit.

[0133] As used herein, the term “network node” may refer to any of a gNB, a gNB-CU, or a gNB-DU, or any combination of them. A RAN (radio access network) node or network node such as, e.g., a gNB, gNB-CU, or gNB-DU, or parts thereof, may be implemented using, e.g., an apparatus with at least one processor and / or at least one memory with processor-readable instructions (“program”) configured to support and / or provision and / or process CU and / or DU related functionality and / or features, and / or at least one protocol (sub-)layer of a RAN (radio access network), e.g., layer 2 and / or layer 3. Different functional splits between the central and distributed units are possible. An example of such an apparatus and components will be described in connection with FIG. 8 below.

[0134] The gNB-CU and gNB-DU parts may, e.g., be co-located or physically separated. The gNB-DU may even be split further, e.g., into two parts, e.g., one including processing equipment and one including an antenna. A central unit (CU) may also be called baseband unit / radio equipment controller / cloud-RAN / virtual-RAN (BBU / REC / C-RAN / V-RAN), open-RAN (O-RAN), or part thereof. A distributed unit (DU) may also be called remote radio head / remote radio unit / radio equipment / radio unit (RRH / RRU / RE / RU), or part thereof. Hereinafter, in various example embodiments of the present disclosure, a network node, which supports at least one of central unit functionality or a layer 3 protocol of a radio access network, may be, e.g., a gNB-CU. Similarly, a network node, which supports at least one of distributed unit functionality or a layer 2 protocol of the radio access network, may be, e.g., a gNB-DU.

[0135] A gNB-CU may support one or multiple gNB-DUs. A gNB-DU may support one or multiple cells and, thus, could support a serving cell for a user equipment (UE) or support a candidate cell for handover, dual connectivity, and / or carrier aggregation, among other procedures.

[0136] The user equipment (UE) 150 may be or include a wireless or mobile device, an apparatus with a radio interface to interact with a RAN (radio access network), a smartphone, an in-vehicle apparatus, an loT device, or a machine-to-machine (M2M) device, among other types of user equipment. Such UE 150 may include: at least one processor; and at least one memory including program code; where the at least one memory and the computer program code are configured to, with the at least one processor, cause the apparatus at least to perform certain operations, such as, e.g., RRC connection to the RAN. An example of components of a UE will bedescribed in connection with FIG. 5. In embodiments, the UE 150 may be configured to generate a message (e.g., including a cell ID) to be transmitted via radio towards a RAN (e.g., to reach and communicate with a serving cell). In embodiments, the UE 150 may generate and transmit and receive RRC messages containing one or more RRC PDUs (packet data units). Persons skilled in the art will understand RRC protocol as well as other procedures a UE may perform.

[0137] With continuing reference to FIG. 1, in the example of a 5G NR network, the network system 100 provides one or more cells, which define a coverage area of the network system 100. As described above, the network system 100 may include a gNB of a 5G NR network or may include any other apparatus configured to control radio communication and manage radio resources within a cell. As used herein, the term “resource” may refer to radio resources, such as a resource block (RB), a physical resource block (PRB), a radio frame, a subframe, a time slot, a sub-band, a frequency region, a sub-carrier, a beam, etc. In embodiments, the network node 120 may be called a base station.

[0138] FIG. 1 provides an example and is merely illustrative of a network system 100 and a UE 150. Persons skilled in the art will understand that the network system 100 includes components not illustrated in FIG. 1 and will understand that other user equipment may be in communication with the network system 100.

[0139] FIG. 2 is a block diagram of example components of the network system 100 of FIG.1. A 5G NR network may be described as an example of the network system 100, and it is intended that aspects of the following description shall be applicable to other types of network systems, as well. The network system may operate in accordance with the signals and connections shown in FIG. 1 such that the UE 150 is in communication with the network system 100 through the radio access network 225. Additionally, the network system may be divided into user plane components and functions and control plane components and functions, as shown and described herein. Unless indicated otherwise, the terms “component,” “function,” and “service” may be used interchangeably herein, and they may refer to and be implemented by instructions executed by one or more processors.

[0140] Example functions of the components are described below. The example functions are merely illustrative, and it shall be understood that additional operations and functions may be performed by the components described herein. Additionally, the connections between components may be virtual connections over service-based interfaces such that any componentmay communicate with any other component. In this manner, any component may act as a service “producer,” for any other component that is a service “consumer,” to provide services for network functions.

[0141] For example, a core network 210 is described in the control plane of the network system. The core network 210 may include an authentication server function (AUSF) 211, an access and mobility function (AMF) 212, and a session management function (SMF) 213. The core network 210 may also include a network slice selection function (NSSF) 214, a network exposure function (NEF) 215, a network repository function (NRF) 216, and a unified data management function (UDM) 217, which may include a uniform data repository (UDR) 224.

[0142] Additional components and functions of the core network 210 may include an application function 218, policy control function (PCF) 219, network data analytics function (NWDAF) 220, analytics data repository function (ADRF) 221, management data analytics function (MDAF) 222, and operations and management function (0AM) 223.

[0143] The user plane includes the UE 150, a radio access network (RAN) 225, a user plane function (UPF) 226, and a data network (DN) 227. The RAN 225 may include one or more components described in connection with FIG. 1, such as one or more network nodes. However, the RAN 225 may not be limited to such components. The UPF 226 provides connection for data being transmitted over the RAN 225. The DN 227 identifies services from service providers, Internet access, and third-party services, for example.

[0144] The AMF 212 processes connection and mobility tasks. The AUSF 211 receives authentication requests from the AMF 212 and interacts with UDM 217 to authenticate and validate network responses to determine successful authentication. The SMF 213 conducts packet data unit (PDU) session management and manages session context with the UPF 226.

[0145] The NSSF 214 may select a network slicing instance (NSI) and determine the allowed network slice selection assistance information (NSSAI). This selection and determination are utilized to set the AMF 212 to provide service to the UE 150. The NEF 215 secures access to network services for third parties to create specialized network services. The NRF 216 acts as a repository to store network functions to allow the functions to register with and discover each other.

[0146] The UDM 217 generates authentication vectors for use by the AUSF 211 and ADM 212 and provides user identification handling. The UDM 217 may be connected to the UDR 224which stores data associated with authentication, applications, or the like. The AF 218 provides application services to a user (e.g., streaming services, etc.). The PCF 219 provides policy control functionality. For example, the PCF 219 may assist in network slicing and mobility management, as well as provide quality of service (QoS) and charging functionality.

[0147] The NWDAF 220 collects data (e.g., from the UE 150 and the network system) to perform network analytics and provide insight to functions that utilize the analytics in the providing of services. The ADRF 221 allows the storage, retrieval, and removal of data and analytics by consumers. The MDAF 222 provides additional data analytics services for network functions. The 0AM 223 provides provisioning and management processing functions to manage elements in or connected to the network (e.g., UE 150, network nodes, etc.).

[0148] FIG. 2 is merely an example of components of a network system, and variations are contemplated to be within the scope of the present disclosure. In embodiments, the network system may include other components not illustrated in FIG. 2. In embodiments, the network system may not include every component illustrated in FIG. 2. In embodiments, the components and connections may be implemented with different connections than those illustrated in FIG. 2. Such and other embodiments are contemplated to be within the scope of the present disclosure.

[0149] Referring to FIG. 3, a diagram illustrating preamble management is shown.

[0150] For example, every cell can provide PRACH resources (e.g., preamble) to its neighboring cell for early timing advance (eTA) acquisition as a contention based eTA acquisition profile, e.g., “CBeTA-Config.” The resources provided are PRACH occasions, preambles, or may be a different PRACH-configuration. Every cell may broadcast a contention-based eTA acquisition profile, e.g., “CBeTA-Config / CB-eTA-PRACHConfig” of its neighbouring cell over the System Information Block (SIB) or indicate with Radio Resource Control (RRC) or a Medium Access Control (MAC) command in dedicated signaling. Serving cell 10 broadcast “CBeTA-Config” of intra- frequency neighbor cells 6, 2 and 5. UE1, UE3 and UE6 can use this profile to send eTA RACH request to neighbor cells 6, 2, and 5 respectively. For example, a geographical representation of UE1, UE3 and UE6 illustrates that it is appropriate for these UE to send eTA RACH request to neighbor cells 6, 2 and 5 respectively. In aspects, every cell may not provide completely unique set of preambles to its neighbors for eTAacquisition because of limited number of preamble available. The present disclosure provides an efficient way to manage and allocate preambles to neighboring cell with partly or fully overlapping set of preambles.

[0151] For example, there may be fully overlapping sets of preambles with more than one (neighboring) cell. Cell 31 may also broadcast profile 1 of neighbor cell 6 with almost the same configurations as cell 10 broadcast profile 1 of neighbor cell 6. UE31 belongs to serving cell 31 and transmits eTA RACH requests to neighbor cell 6. UE1 belongs to serving cell 10 and transmits eTA RACH requests to neighbor cell 6. For example, both UEs may (co-incidentally) use the same RACH preamble (PRACH frame and / or occurrence), but neighbor cell 6 may distinguish the UEs and their serving cell, for example, based on the incoming direction of each UE’s RACH request. In this way, neighboring cell 6 can efficiently manage its preamble for eTA acquisition procedure: neighboring cell 6 can give the same eTA RACH preamble to any neighboring cells as long as neighboring cell 6 can distinguish which cell is used by the UE for the eTA request

[0152] In another example, there may be partially overlapping sets of preambles with more than one neighboring cell. Neighboring cell 2 has provided its preamble set (6, 7, 8, 9, 10) to cell 10. The neighboring cell 5 has provided its preamble set (6, 7, 12, 14, 15) to serving cell 10. UE3 and UE6 co-incidentally use preamble 6 to send eTA RACH request with same PRACH resource to cell 10. But cell 10 can distinguish the incoming eTA RACH request based on RACH direction. Thus, the disclosed system enables (neighboring) overlapping preamble allocation to neighboring cells to be efficiently managed. For example, if UE1 (belongs to serving cell 10), reads UEl’s SIB for Profile 1 of cell 6 and get eTA RACH request configurations. If UE1 finds that the measurement of cell 6 is above a measurement threshold (e.g., measThreshold), and cell priority and the cell number of the profile allow UE1 to send an eTA RACH request to cell 6. As UE has sent eTA RACH request to get eTA, the UE does not need to wait for response from cell 6. As cell 6 can recognize the preamble and understand that it is for eTA acquisition, cell need not to respond with RAR but store the estimated TA (based on eTA RACH) against used preamble resource (preamble, RACH occasion etc.). Cell 6 can provide stored TA to UE during HO preparation / execution.

[0153] FIGS. 4 A and 4B is a diagram of an example embodiment of signals and operations among a UE, a serving cell and a target cell according to one illustrated aspect of the disclosure. In various embodiments, FIGS. 4A and 4B show an example method of sending eTA RACH request with cell-specific configurations, by user equipment (UE), to a source network node (source gNB) and a target network node (target gNB, neighboring cell), according to one illustrated aspect of the disclosure. In various embodiments, the components depicted in FIGS. 4A and 4Bmay correspond to similar components described above in FIGS. 1 and 2. It will be understood that a described signal may have associated operations, and a described operation may have associated signals.

[0154] At operation 401, a user equipment (UE) receives from a source network node that is serving a source cell, a broadcast signal including an early timing advance (eTA) configuration for a neighboring cell. The neighbor cell may become a target cell, for example, for handover (HO) purposes, dual connectivity, carrier aggregation, or sidelink, or may be provided by a target network node different from the source cell node. Although described as a single cell, it will be understood that there may be more than one neighboring cell(s) supporting eTA for RACH-less HO and serving cell(s) will broadcast eTA configurations for all neighboring cell(s).

[0155] The eTA configuration may include an indication of an eTA threshold and a contentionbased random access (CBRA) resource associated with the neighboring cell. The CBRA resource includes PRACH information, including a preamble, a RACH occasion, and / or a RACH frame timing. For example, the source cell may be broadcasting system information (e.g., SIB1), for example, CB-eTA-PRACHConfig {1.. to n of neighboringCell-PRACH information}, where: neighboringCell-PRACH information = {PRACH related info of neighboring cell}, where n = max num of neighboring cell to perform eTA.

[0156] UE’s interested in CBRA based eTA request, may read and / or use this information to send CBRA based eTA request to a relevant neighboring cell without any explicit dedicated messaging between UE, source and neighbor cell to receive (from a neighbor cell) and assign (to the UE) PRACH config information.

[0157] cellSpecific-eTA-Threshold: This threshold is used by the UE to evaluate the candidate target cell to send eTA request. If the UE determines that the measurement of the target cell is above this cell specific threshold, it means that neighbor cell is eligible as a candidate target cell and thus for eTA requisition and the UE transmits eTA requests to the candidate target cell(s),

[0158] eTAReqReportTimer: This timer helps the UE to send eTA requests to the candidate cell and inform the source cell in a timely manner. This timer will help to detect the contention if more than one UE is using the same PRACH info at the same time to send an eTA request to a candidate cell. This timer will be running in the network (the source cell), and the UEs are generally expected to send measurement reports with PRACH information within this period.

[0159] This information may be broadcast over SIB1. However, in case this information is being broadcasted over any other SIB (other SIBs are optional SIBs), then “CB-eTA-support“ flag over SIB1 is included. SIB1 may be a mandatory SIB and would be read by all the UEs. “CB-eTA-support “flag over SIB1 over SIB1 may be an indication to all UEs that NW supports eTA acquisition, and other information for this feature is available in other relevant SIB. So that interested UE’s could read that relevant information after reading mandatory SIB1.

[0160] In another aspect, this information may be transmitted to UEs. The network can send this information to the UE in the dedicated message (preferably over RRCSetup / RRCReconfiguration) preferably during the UEs attach / TA / RA -update procedure . So that UE keeps this information in hand to be used whenever needed.

[0161] Operations 402 to 405 depict the UE in connected RRC mode with the source cell, data transmission and / or reception between the source cell and the UE is going on. The source cell has provided measurement configurations to the UE and the UE performs measurements with all configured cell(s).

[0162] At operation 406, the source cell starts the eTA request report timer (eTAReqReport timer). The source cell expects the UE to report measurement results with eTA request details (PRACH info used to send eTA RACH requirement) prior to the expiration of this timer.

[0163] At operations 407 and 408, the UE performs measurements of the target cells.

[0164] At operation 409, the UE evaluates the neighboring cell measurement with a cellspecific eTA threshold, and if the condition is met, where the UE finds that the respective neighboring cell(s) is a candidate for eTA acquisition. This provides the benefit of when UE is performing the measurement of the neighboring cell(s) at that time the UE is already in Sync (at least downlink (DL) sync) with that neighboring cell, UE can utilize this in-sync state to send eTA request to that neighboring cell(s). In this way, the UE can save synchronization procedure, timing, and power associated with performing synchronization with neighboring cell(s) for sending eTA requests.

[0165] At operation 409, the UE determines if the measurement is equal to or greater than the cell-specific eTA threshold.

[0166] At operation 410, the UE selects the PRACH resource from SIB(l) and transmits the CBRA requirements to the source cell. For example, the UE may use SIB(l)-> CB-eTA-PRACHConfig-> cellSpecific-eTA- Threshold to evaluate if the neighbor cell is eligible foracquire eTA. If evaluation is positive, UE can use “CB-eTA-PRACHConfig” and information to send PRACH to neighboring cell(s).

[0167] “cellSpecific-eTA- Threshold” enables the UE to evaluate the candidate target cell(s) without any explicit signaling between UE and source. In this way, along with other attributes like cell priorities and / or a maximum number of cells to perform eTA, the source cell can limit the eTA acquisition to a certain number of target cells only. This provides the benefit of minimizing the cost associated with (for example, in terms of PRACH resource, signaling and delay associated) sending the eTA request to each target cell. Otherwise the UE may transmit an eTA request to all cells for which the UE is configured to perform the measurement for prospective HO.

[0168] At operations 412 and 414, the UE transmits CBRA- based eTA requests to eligible candidate(s) cells. The UE has used the “CB-eTA-PRACHConfig” information and transmitted eTA request to neighboring cell thus UE need not to wait for RAR and other procedure.

[0169] In aspects, operations 407, 408, 409, 410, 411, 412 and 414 may be happening simultaneously.

[0170] At operations 413 and 415, the neighboring cell may recognize the incoming CBRA request based on the preamble that the neighboring cell has allocated for eTA acquisition. Neighboring cell(s) may not need to respond with RAR and other procedures. Neighboring cells(s) may store the evaluated TA with associated PRACH info(PRACH information used in CBRA Req) so that the neighboring cell can recognize the appropriate UE during the handover preparation phase.

[0171] The disclosed systems and methods provide the benefit of time off air saving of CFRA-based eTA acquisition without the associated cost of (additional signaling over Xn and Uu and delays involved) in assigning CFRA PRACH resources and / or saving air interface resources used in CFRA based eTA acquisition.

[0172] At operation 416, the UE transmits the measurement report(s) with the “PRACH information” used to send eTA requests for each eligible cell(s), such as a preamble, a RACH occasion, and / or a RACH frame timing.

[0173] At operation 417, the source cell makes the handover decision. In aspects, the source cell can prioritize the candidate cell for handover preparations if the UE has reported the PRACH information with a measurement report for the cell(s). This is an indication to source cell that UEhas requested for eTA and could perform RACH-less HO with these cell(s). The source cell can prioritize these cells for HO preparation because there would be RACH-less HO with these cells.

[0174] At operation 418, the timer (eTAReqReportTimer) expires. The source cell expects the UE to report measurement results with PRACH information to be reported within this period.

[0175] At operation 419, The source cell transmits a handover request with “PRACH information” and other legacy contents to the target cell for handover preparation.

[0176] At operations 420 and 421: The source cell recognizes the incoming Handover preparation request and associated UE with provided “PRACH information,” and provides the stored TA in the handover command message to UE via the source cell piggybacked in handover request acknowledgment.

[0177] At operation 422, the source cell transmits to the UE an RRC reconfiguration request and handover command.

[0178] At operation 423, the UE does not perform the RACH procedure.

[0179] At operation 424, the UE transmits to the target cell an RRC reconfiguration complete message.

[0180] For example, system information (preferably SIB1), is providing cell specific cellSpecific-eTA-Threshold (common to all the UEs) and eTAReqReportTimer. As these values are common to all the UEs. There could be different conditions associated with different UEs including: speed class, location, measurement reporting offset, etc., with the above dynamics. Cellspecific cellSpecific-eTA- Threshold, timer values, and target cell priority could not be an efficient attribute to trigger eTA request to candidate cells.

[0181] In an example, a UE is on the north side of the serving cell, so neighboring cells' priority, which is located on the south side of the UEs, is not applicable, cell-specific threshold value could not be the same for a UE in the high-speed class compared to a UE in low-speed class.

[0182] In aspects, there may be no TA acquisition is required for any co-located cell, that is, the UE may use TA=0 or UE estimated TA. In aspects, there could be different scenarios where, the network can better instruct (specifically) to a UE about attributes / offset / timers / priorities about neighboring cell so that UE can efficiently send the eTA request.

[0183] The operations of FIGS. 4A and 4B are merely illustrative, and variations are contemplated to be within the scope of the present disclosure. In embodiments, the operations may include other operations not illustrated in FIGS. 4A and 4B. In embodiments, the operations maynot include every operation illustrated in FIGS. 4A and 4B. In embodiments, the operations may be implemented in a different order than that illustrated in FIGS. 4 A and 4B. Such and other embodiments are contemplated to be within the scope of the present disclosure. Persons of skill in the art will appreciate that, although various example components are described as performing various functions, other components may perform those functions described in FIGS. 4A and 4B.

[0184] The following describes operations from the perspective of a UE. From such a perspective, a method may include: receiving, by a user equipment (UE) from a source network node providing a source cell, a broadcast signal including an early timing advance (eTA) configuration for a neighboring cell, wherein the eTA configuration includes an indication of an eTA threshold and a contention-based random access (CBRA) resource associated with the neighboring cell, and wherein the CBRA resource includes PRACH information including at least one of a preamble, a RACH occasion, or a RACH frame timing (e.g., FIG. 4A, step 401); measuring, by the UE, at least one of a reference signal received power (RSRP) of a reference signal of the neighboring cell, a priority of the neighboring cell, or a number of the neighboring cell to perform eTA (e.g., FIG. 4A, steps 407 and 408); and transmitting a random access request towards the neighboring cell using the CBRA resource, in response to determining the measured RSRP being above the eTA threshold (e.g., FIG. 4A, steps 409 and 410).

[0185] The following describes operations from the perspective of a source network node. From such a perspective, a method may include: transmitting, by a source network node providing a source cell to a user equipment (UE), a broadcast signal including an early timing advance (eTA) configuration for a neighboring cell, wherein the eTA configuration includes an indication of an eTA threshold and a contention-based random access (CBRA) resource associated with the neighboring cell, wherein the CBRA resource includes PRACH information including: a preamble, a RACH occasion, and / or a RACH frame timing (e.g., FIG. 4A, step 401); and receiving, by the source network node, a random access request towards the neighboring cell using the CBRA resource, in response to determining a measured reference signal received power (RSRP) being above the eTA threshold (e.g., FIG. 4A, steps 409 and 410).

[0186] FIGS. 5 A and 5B is a diagram of an example embodiment of signals and operations among a UE, a serving cell and a target cell according to one illustrated aspect of the disclosure. In various embodiments, FIGS. 5A and 5B show an example method of to enable a user equipment (UE), to send eTA acquisition based on UE specific configurations, to a source network node(source gNB), and a target network node (target gNB, neighboring cell), according to one illustrated aspect of the disclosure. In various embodiments, the components depicted in FIGS. 5A and 5B may correspond to similar components described above in FIGS. 1 and 2. It will be understood that a described signal may have associated operations, and a described operation may have associated signals.

[0187] Referring to operations 502-512 the serving cell broadcasts cell specific eTA configurations. Operations 502-504 are similar to operations 402-404 of FIGS. 4A and 4B. The UE is in RRC connected state with source cell and data trans-reception is occurring.

[0188] At operation 505, the source cell transmits to the UE specific eTA configurations over RRC connection reconfigurations while providing measurement configurations.

[0189] At operation 506, the source cell transmits to the UE an RRC reconfiguration message configuration. The message may include: SB1 (only RACH-related confirmation / complete e.g., configuration), eTA threshold for CBRA for eTA, UE specific eTA threshold, target cell prioritization, number of target cells for eTA RA requirement, and / or an indication of implicit: no RACH for co-located cell.

[0190] The source cell may choose to assign eTA configuration along with the measurement configuration as described above. By evaluating neighboring cells during measurements, the UE can determine if a cell qualifies (based on criteria provided to the UE) as a candidate for sending an eTA request. Thus, the UE can transmit the eTA to the source cell and save time. This provides the benefit of when the UE is performing the measurement of the neighboring cell(s) at that time the UE is already in synchronization (at least DL synchronization) with that neighboring cell; the UE can utilize this in-sync state to send eTA request to that neighboring cell(s). In this way, the UE can save (explicitly) the Sync procedure and timing and power associated with it while performing synchronization with neighboring cell(s) for sending an eTA request. The UE performs neighboring cell measurements as per the provided configurations.

[0191] At operations 509 and 510, the UE evaluates the candidate target cell to transmit an eTA request based on UE-specific configurations. If the neighboring cell evaluation for eTA request is successful, the UE sends a CBRA-based eTA request to that neighboring cell during the measurement.

[0192] At operation 511 , the target (candidate) cell may recognize the incoming CBRA request based on PRACH-resource used and store the estimated TA with PRACH information.

[0193] The target cell and the UE do not wait for further steps of the CBRA procedure, as these steps are for eTA acquisition.

[0194] At operation 513, the UE provides a measurement report with PRACH information used for eTA requests to the source cell. The source cell may transmit PRACH information to the candidate cell during handover (HO) preparation so that the candidate cell recognizes the UE and provides the stored (with PRACH information) TA to the UE via the source cell.

[0195] Referring to operations 513-518, the source cell can evaluate the UE-specific conditions and configurations for eTA acquisition.

[0196] At operation 513: the UE transmits the measurement reports to the source cell. Measurement reports include measurement results of candidate cell(s) and preambles used for eTA.

[0197] Operation 514 depicts the handover (HO) decision based on provided measurement reports (operation 513) the source cell can choose potential candidate cell(s) to perform eTA acquisition based on many criteria like measurement results, cell priorities (intra-frequency cell is preferable than inter frequency Cell, the UEs ongoing service and candidates’ capabilities) to select candidate cell(s).

[0198] At operations 515 and 516, the source cell assigns UE-specific eTA acquisition configuration, including threshold, offset, cell priority, and number of candidates cell, and informs UE to use provided UE-specific configurations or UE evaluated / measured TA, TA=0, TA=source instructions, in PDCCH order.

[0199] At operations 517 and 518, the UE transmits CBRA-based eTA requests to the selected target (candidate) cell. The target cell can recognize the incoming CBRA request based on the PRACH-resource used and store the estimated TA with PRACH information.

[0200] The target cell and the UE do not wait for further steps of CBRA procedure as the further steps are for eTA acquisition.

[0201] After operation 518, the procedure follows operations 419-424 of FIG. 4B.

[0202] Operations 513-518 provide the benefit of where the UE has already reported the measurement results of neighboring cells to the source cell, enabling the source cell to select the target cells (e.g., based on neighboring cells priority, UEs speed and directi on / locati on, and / or number of cell for the eTA request) for eTA acquisition and instruct the UE.

[0203] While in operations 502-512, the network informs the UE about neighboring cells' priority, a number of cells for eTA request, the cell-specific threshold to the UE, and the UE decides the candidate cell to perform eTA based on the provided information.

[0204] UE-specific eTA configurations (provided via RRC reconfigurations / PDCCH order) are superset configurations, and the UE overwrites these configurations on cell-specific configurations.

[0205] The operations of FIGS. 5 A and 5B are merely illustrative, and variations are contemplated to be within the scope of the present disclosure. In embodiments, the operations may include other operations not illustrated in FIGS. 5 A and 5B. In embodiments, the operations may not include every operation illustrated in FIGS. 5A and 5B. In embodiments, the operations may be implemented in a different order than that illustrated in FIGS. 5A and 5B. Such and other embodiments are contemplated to be within the scope of the present disclosure. Persons of skill in the art will appreciate that, although various example components are described as performing various functions, other components may perform those functions described in FIGS. 5 A and 5B.

[0206] The following describes operations from the perspective of a UE. From such a perspective, a method may include: receiving, by a user equipment (UE) from a source network node providing a source cell, a radio resource control (RRC) message including a first early timing advance (eTA) configuration for a neighboring cell and a measurement configuration for a neighboring cell, wherein the first eTA configuration includes an indication of an eTA threshold and a contention-based random access (CBRA) resource associated with the neighboring cell, and wherein the CBRA resource includes PRACH information including at least one of a preamble, a RACH occasion, or a RACH frame timing (e.g., FIG. 5A, step 501); measuring, by the UE, at least one of a reference signal received power (RSRP) of a reference signal of the neighboring cell, a priority of the neighboring cell, or a number of the neighboring cell (e.g., FIG. 5A, steps 506 and 509); and transmitting a random access request towards the neighboring cell using the CBRA resource of the first eTA configuration, in response to determining the measured RSRP being above the eTA threshold of the first eTA configuration (e.g., FIG. 5B, step 520).

[0207] The following describes operations from the perspective of a source network node. From such a perspective, a method may include: transmitting, by a source network node providing a source cell to a user equipment (UE), a radio resource control (RRC) message including a first early timing advance (eTA) configuration for a neighboring cell and a measurement configurationfor a neighboring cell, wherein the first eTA configuration includes an indication of an eTA threshold and a contention-based random access (CBRA) resource associated with the neighboring cell, and wherein the CBRA resource includes PRACH information including at least one of a preamble, a RACH occasion, or a RACH frame timing (e.g., FIG. 5A, step 501); and receiving, by the source network node, a random access request towards the neighboring cell using the CBRA resource, in response to determining a measured reference signal received power (RSRP) being above the eTA threshold (e.g., FIG. 5B, step 520).

[0208] The following describes operations from the perspective of a UE. From such a perspective, a method may include: transmitting, from a user equipment (UE) to a source network node providing a source cell, a message including a measurement report related to a neighboring cell; receiving, by the UE from the source network node providing the source cell, a physical downlink control channel (PDCCH) order to send an early timing advance (eTA) request to the neighboring cell, wherein the PDCCH order includes at least one of a priority of the neighboring cell or a number of the neighboring cell (e.g., FIG. 5B, step 513); and transmitting, by the UE, a contention-based random access (CBRA) eTA request to the neighboring cell (e.g., FIG. 5B, steps 515-517).

[0209] The following describes operations from the perspective of a source network node. From such a perspective, a method may include: receiving, by a source network node providing a source cell, a message including a measurement report related to a neighboring cell (e.g., FIG. 5B, step 513); determining, by the source network node providing the source cell, that a measured reference signal received power (RSRP) is above an eTA threshold based on the measurement report (e.g., FIG. 5B, step 514); and transmitting, by the source network node providing the source cell to a user equipment (UE), a physical downlink control channel (PDCCH) order to send an early timing advance (eTA) request to the neighboring cell, wherein the PDCCH order includes at least one of a priority of the neighboring cell or a number of the neighboring cell (e.g., FIG. 5B, step 517).

[0210] FIGS. 6A-6C are a diagram of an example embodiment of signals and operations among a UE, a serving cell and a target cell according to one illustrated aspect of the disclosure. In various embodiments, FIGS. 6A-6C show an example method of eTA contention detection by a source network node (source gNB), according to one illustrated aspect of the disclosure. In various embodiments, the components depicted in FIGS. 6A-6C may correspond to similarcomponents described above in FIGS. 1 and 2. It will be understood that a described signal may have associated operations, and a described operation may have associated signals.

[0211] Operations 601 to 604 are the same as operations 401-404 of FIGS. 4A and 4B.

[0212] Operation 605 depicts that the network has provided CBRA-based eTA acquisition resources to each UE (e.g., UE1 and UE2), and each UE has transmitted eTA RACH to the network.

[0213] At operation 606, the source cell starts the eTA request report timer (eTAReqReport timer).

[0214] In aspects, the eTA configuration may be a cell-based eTA configuration (CBeTA-Config) and may further include the following information:CBeTA-Config{Cell id : integer;preamblelndex :: {1,2, 3, 4, 5}otherResources : : rach-occ; — optionalmeasThreshold;Cell priority; — optionalNumber of cell for eTA - optional

[0215] The CBeTA-Config may be a superset information element (IE) containing eTA RACH request related configurations. Cell ID is a neighboring cell ID for which the profile and configurations belong to. preamblelndex is a preamble index of a neighboring cell that can be used to send an eTA RACH request to a relevant neighboring cell. Rach-occ is rach occasion details of the neighboring cell which the UE can use to send an eTA RACH request. In aspects, the CBeTA-Config may include a measurement threshold (measThreshold) and / or eTA threshold, which is a cell specific eTA threshold. For example, in a case where the UE determines that the measurement result of the neighboring cell is above the cell-specific eTA threshold, the neighboring cell is eligible to perform eTA acquisition, and the UE can transmit the eTA RACH request. In aspects, the CBeTA-Config may further include cell priority and / or target cell prioritization, indicating the priority of the cell to perform eTA acquisition. For example, in a case where many cells are eligible for eTA based on measThreshold, the UE can transmit eTA RACH to high-priority cells up to a number of the cells for eTA. In aspects, the CBeTA-Config may further include a number of cellsfor eTA, which indicates a number of cells to perform eTA acquisition based on the cell priority. In aspects, the CBeTA-Config may further include an eTA request report timer, where the UEs are expected to report the PRACH-info (e.g., preamble, RO, and / or frame number) in a measurement report source cell within an eTA request report time period.

[0216] In aspects, the CBeTA-Config may further include a counter value, which is the maximum number of retries allowed for eTA requests. The UE may perform the retry based on the evaluation as mentioned in operation 719 of FIG. 7.

[0217] At operations 607 and 608, each UE transmits CBRA based RACH to the target (candidate) cell.

[0218] Operation 609 depicts the contention detection at source cell. The source cell received a measurement report containing same PRACH information from two (or more) UEs within a specific time period

[0219] At operations 610 and 611, each UE transmits a measurement report with PRACH information (used at operations 607 and 608) to the source cell.

[0220] Operation 612 depicts that the source cell has received more than one measurement report with the same PRACH information within the eTAReqReport period and that there is contention for a CBRA-based eTA request.

[0221] At operation 613, the source cell detects the contention for CBRA based eTA acquisition request.

[0222] Operation 614 depicts an example solution for contention resolution, where the source orders the UEs to repeat eTA measurements with CBRA.

[0223] At operations 615 and 616, the source transmits a PDCCH order to each of the UEs to retry for eTA acquisition because of contention. The source takes account of criteria including each UE’s speed, DL RF condition, UL RF condition, and / or service type each UE is subscribed to, and provides the RACH type (e.g., CBRA in the PDCCH order) to perform eTA acquisition.

[0224] At operation 617, each UE retries for eTA request and transmits measurement reports with PRACH information to the source.

[0225] Operation 618 depicts an example solution for contention resolution where the source issues a CFRA PDCCH order in time staged manner.

[0226] At operations 619 and 621, the source cell issues PDCCH order with neighbor cells PRACH resource for CFRA based eTA. The serving cell may reserve some of the RACH resource(preamble) for CFRA based eTA.

[0227] At operations 620 and 622: each UE transmits a CFRA based eTA request to the target (candidate) cell.

[0228] At operations 623 and 624, the source cell transmits a HO request message with PRACH information to the target cell. The source cell transmits to the target cell, PRACH information as received in measurement reports (operations 610 and 611) or as assigned in operations 619 and 621.

[0229] Operation 625 depicts an example solution for contention resolution where the source cell informs the target cell about contention.

[0230] At operation 625, the source cell makes the handover decision. At operation 626, the source cell determines if the HO request with PRACH information is transmitted to the target cell. At operation 627, the handover request is transmitted by the source cell to the target cell. At operation 628, the handover request acknowledgment is transmitted from the target cell to the source cell.

[0231] At operation 628, the source PRACH information and contention detected flag to the target cell in the HO request message. The source cell can wait until the eTAReqReport timer elapses before sending an HO request to the target cell. In an aspect, the source cell may transmit an HO request as soon as the measurement report is received and the HO decision is made. In aspects, the source cell may transmit an HO request message with PRACH information (received in the measurement report), and in case the source cell receives another measurement report with the same PRACH information within the eTAReqReport period, the source cell transmits an HO request as explained in operation 628. The benefit of this lateral approach is that HO preparation is carried out as soon as the measurement report is received and the HO decision is made. But in a formal case, the source cell has to wait for eTAReqReport period before it transmits the HO request message to the target cell.

[0232] At operation 629, the target cell transmits to the UE a HO request acknowledgment with a flag indicating fallback to RACH-based HO.

[0233] At operations 630 and 631, the source cell transmits a RRC reconfiguration request piggybacking the HO command received from the target cell, to the UE. The source cell mayoptionally include a fallback to RACH based HO flag in the RRC reconfiguration message. In this case, the target cell has already sent HOCommand in HO request acknowledgement message to the source cell before the target cell receives the message of operation 628.

[0234] Operations 629 to 636 illustrate the remaining handover operations, although a difference is that the UE is not performing the RACH procedure but instead directly sending the HO completion message to the target cell.

[0235] The operations of FIGS. 6A-6C are merely illustrative, and variations are contemplated to be within the scope of the present disclosure. In embodiments, the operations may include other operations not illustrated in FIGS. 6A and 6B. In embodiments, the operations may not include every operation illustrated in FIGS. 6A and 6B. In embodiments, the operations may be implemented in a different order than that illustrated in FIGS. 6A and 6B. Such and other embodiments are contemplated to be within the scope of the present disclosure. Persons of skill in the art will appreciate that, although various example components are described as performing various functions, other components may perform those functions described in FIGS. 6A and 6B.

[0236] The following describes operations from the perspective of a UE. From such a perspective, a method may include: receiving, by a first user equipment (UE) from a source network node providing a source cell, a broadcast signal including an early timing advance (eTA) configuration for a neighboring cell, wherein the eTA configuration includes an indication of an eTA threshold, a contention-based random access (CBRA) resource associated with the neighboring cell, a preamble, a priority of a target network node, and a number of nodes to perform eTA associated with the neighboring cell (e.g., FIG. 6A, step 601); measuring, by the first UE, a reference signal received power (RSRP) of a reference signal of the neighboring cell (e.g., FIG.6 A, step 609); and transmitting, by the first UE to the source network node, a measurement report including PRACH information, wherein the PRACH information includes a preamble, a RACH occasion, and a RACH frame timing, wherein the PRACH information is the same as a second UE within a predetermined time period (e.g., FIG. 6 A, steps 610 and 611).

[0237] The following describes operations from the perspective of a source network node. From such a perspective, a method may include: transmitting, by a source network node to a first user equipment (UE) and to a second UE, a broadcast signal including an early timing advance (eTA) configuration for a neighboring cell, wherein the eTA configuration includes an indication of an eTA threshold, a contention-based random access (CBRA) resource associated with theneighboring cell, a preamble, a priority of a target network node, and a number of nodes to perform eTA associated with the neighboring cell (e.g., FIG. 6A, step 601); and receiving, by the source network node, a measurement report including PRACH information, wherein the PRACH information includes a preamble, a RACH occasion, and a RACH frame timing, wherein the PRACH information is the same as the second UE within a predetermined time period (e.g., FIG.6A, steps 610 and 611).

[0238] FIGS. 7A-7F are a diagram of an example embodiment of signals and operations among a UE, a serving cell and a target cell according to one illustrated aspect of the disclosure. In various embodiments, FIGS. 7A-7D show an example method of the CBRA based eTA contention detection at a source network node (source gNB) and resolution, according to one illustrated aspect of the disclosure. In various embodiments, the components depicted in FIGS.7A-7F may correspond to similar components described above in FIGS. 1 and 2. It will be understood that a described signal may have associated operations, and a described operation may have associated signals.

[0239] Operations 701 to 705 are the same as operations 601-605 of FIG. 6A.

[0240] At operations 706 and 708: UEs send CBRA eTA request to the target cell.

[0241] At operation 707, the target cell starts eTAReqReport timers as soon as the target cell receives an eTA request with PRACH info.

[0242] The UEs are supposed to send measurement report to source and source is supposed to send HOI request message to the target cell with specific period. If two UEs are co-incidentally using the same preamble and PRACH resources to send eTA request to the target cell, it is expected that the UE and the source cell will send measurement request to the source cell and HO request message (with PRACH information) to the target cell respectively within same time period.

[0243] The target cell, after receiving an eTA request message with PRACH information, waits for the eTAReqReport period to receive another eTA req with the same PRACH resource. In this case the target cell receives more than one eTA request with the same PRACH information within the eTAReqReport period. This means contention has occurred, and the target cell has detected that contention. The target cell may wait for operations 713 and 715.

[0244] Operations 710 and 711 are similar to operations 610 and 611 of FIGS 6A.

[0245] Operation 712 depicts the contention detection at the target cell (based on info explained in operation 707).

[0246] At operations 713 and 714, the target cell receives an HO request message from each UE, with the same PRACH information within a specific period.

[0247] At operation 715, the contention is detected by the target cell and the target cell recognizes the UEs are causing contention.

[0248] Operation 716 illustrates contention resolution based on a re-try mechanism.

[0249] At operation 717, as the target cell has detected the contention among the UEs, the target cell does not transmit the HO request acknowledgment (HO command) message to the UEs involved in contention.

[0250] At operation 718, the UEs do not receive the HO command message from the source cell within specific periods.

[0251] At operations 719 to 722, each UEs checks (e.g., evaluates) for an eTA request counter value and re-sends eTA request to the target cell.

[0252] Operations 723 to 732 are similar to operations 623 to 632 of FIGS. 6A and 6B (these are just repetitions as a retry mechanism).

[0253] Operation 733 illustrates another example of contention resolution: Fallback to RACH-based HO.

[0254] At operation 734 to 737, the target cell transmits an HO request acknowledgement message with fallback to a RACH-based HO (if the target cell does not transmit TA in the HO command message, this is an indication of RACH-based HO). The source cell forwards the message to the UE respectively.

[0255] Operation 738 is another example of a contention resolution solution, illustrating fallback to CFRA-based eTA acquisition.

[0256] At operation 739, the target cell transmits to the source cell an HO request acknowledgment message.

[0257] At operation 740, the source cell performs RRC reconfiguration preparation for TA acquisition.

[0258] At operation 741, the source cell transmits to the first UE an RRC reconfiguration message with an eTA acquisition grant.

[0259] At operation 742, the first UE transmits to the source cell an RRC reconfiguration acknowledgment message. At operation 743, the first UE triggers eTA acquisition.

[0260] At operation 744, the target cell performs TA computation and generates RRC configuration for the UE to execute the cell switch.

[0261] At operation 745, the target cell transmits to the source cell a TA metric with the full RRC configuration.

[0262] At operation 746, the source cell completes the RRC reconfiguration preparation, including the freshly acquired TA metric.

[0263] At operation 747, the source cell transmits to the first UE a HO command message with the TA metric.

[0264] The operations of FIGS. 7A-7F are merely illustrative, and variations are contemplated to be within the scope of the present disclosure. In embodiments, the operations may include other operations not illustrated in FIGS. 7A-7F. In embodiments, the operations may not include every operation illustrated in FIGS. 7A-7F. In embodiments, the operations may be implemented in a different order than that illustrated in FIGS. 7A-7F. Such and other embodiments are contemplated to be within the scope of the present disclosure. Persons of skill in the art will appreciate that, although various example components are described as performing various functions, other components may perform those functions described in FIGS. 7A-7F.

[0265] The following describes operations from the perspective of a UE. From such a perspective, a method may include: receiving by a first user equipment (UE) from a source network node, a broadcast signal including an early timing advance (eTA) configuration for a neighboring cell, wherein the eTA configuration includes an indication of an eTA threshold, a contention-based random access (CBRA) resource associated with the neighboring cell, a preamble, a priority of a target network node, and a number of nodes to perform eTA (e.g., FIG. 7A, step 701); measuring, by the first UE, a reference signal received power (RSRP) of a reference signal of the neighboring cell (e.g., FIG. 7A, step 710); and transmitting, by the first UE to the target network node, a CBRA based RACH request for eTA acquisition prior to the target network node starting an eTA requirement report timer, wherein the target network node is configured to expect the first UE and a second UE to report measurement results with PRACH information used to send eTA RACH requirements prior to an expiry of the eTA requirement report timer (e.g., FIG. 7B, steps 712-714).

[0266] The following describes operations from the perspective of a target network node. From such a perspective, a method may include: receiving, by a target network node from a first UE, aCBRA based RACH request for eTA acquisition prior to the target network node starting an eTA requirement report timer, wherein the target network node is configured to expect the first UE and a second UE to report, to a source network node serving a source cell, measurement results with PRACH information used to send eTA RACH requirements prior to an expiry of the eTA requirement report timer to enable the source network node to send a handover request to the target network node (e.g., FIG. 7A. step 701); receiving, by the target network node for each of the first UE and a second UE, within a predetermined time period, a handover request message from a source network node including PRACH information, the PRACH information including a preamble, a RACH occasion, a RAC frame, and timing, wherein the PRACH information from the first UE is the same as the PRACH information from the second UE (e.g., FIG. 7A, steps 710 and 711); and detecting, by the target network node, a contention caused by the first UE and the second UE (e.g., FIG. 7B, steps 712-714).

[0267] sThe disclosed features provide the benefits of enabling the efficient unitization of PRACH-resources. Preamble resources are assigned to neighboring cells in such a way that the cell can recognize the incoming CBRA Req is for eTA, and neighboring cell & UE need not perform RAR and other procedures. The neighboring cell could recognize that the incoming request is from which neighboring cell because the cell is aware of which preambles are assigned to which neighboring cell; thus, the cell can use this information to recognize the neighboring cell from which the UE belongs and send the request. This way, which kind of cell (intra / inter-frequency and / or inter-RAT). The disclosed features can reduce the signaling overhead involved in preamble fetching and assignment to UE, and yet can reap the benefit of CFRA-based eTA acquisition. The UE and the source cell can limit the eTA acquisition to a certain number of candidate cells with the help of “cellSpecific-eTA-Threshold.” The disclosed features help the UE to evaluate the candidate cells for eTA without any explicit signaling with the source cell.

[0268] FIG. 8 is a block diagram of a wireless station or node (e.g., UE, user device, AP, BS, eNB, gNB, RAN node, network node, TRP, or other node) 800, according to one illustrated aspect of the present disclosure. The wireless station 1200 may include, for example, one or more (e.g., two as shown in FIG. 8) RF (radio frequency) or wireless transceivers 802A, 802B, where each wireless transceiver includes a transmitter to transmit signals and a receiver to receive signals. The wireless station also includes a processor or control unit / entity (controller) 804 to execute instructions or software and control transmission and receptions of signals, and a memory 1206 tostore data and / or instructions.

[0269] Processor 804 may also make decisions or determinations, generate frames, packets or messages for transmission, decode received frames or messages for further processing, and other tasks or functions described herein. Processor 804, which may be a baseband processor, for example, may generate messages, packets, frames, or other signals for transmission via wireless transceiver 802 (802A or 802B). Processor 804 may control transmission of signals or messages over a wireless network and may control the reception of signals or messages, etc., via a wireless network (e.g., after being down-converted by wireless transceiver 802, for example). Processor 804 may be programmable and capable of executing software or other instructions stored in memory or on other computer media to perform the various tasks and functions described above, such as one or more of the tasks or methods described above. Processor 804 may be (or may include), for example, hardware, programmable logic, a programmable processor that executes software or firmware, and / or any combination of these. Using other terminology, processor 804 and transceiver 802 together may be considered as a wireless transmitter / receiver system, for example.

[0270] In addition, referring to FIG. 8, a controller (or processor) 1208 may execute software and instructions, and may provide overall control for the station 800, and may provide control for other systems not shown in FIG. 8, such as controlling input / output devices (e.g., display, keypad), and / or may execute software for one or more applications that may be provided on wireless station 800, such as, for example, an email program, audio / video applications, a word processor, a Voice over IP application, or other application or software.

[0271] In addition, a storage medium may be provided that includes stored instructions, which when executed by a controller or processor may result in the processor 804, or other controller or processor, performing one or more of the functions or tasks described above.

[0272] According to another example embodiment, RF or wireless transceiver(s) 802A / 802B may receive signals or data and / or transmit or send signals or data. Processor 804 (and possibly transceivers 802A / 1202B) may control the RF or wireless transceiver 802A or 802B to receive, send, broadcast or transmit signals or data.

[0273] Example embodiments are provided or described for each of the example methods, including: An apparatus (e.g., 800, FIG. 8) including means (e.g., processor 804, RF transceivers 802A and / or 802B, and / or memory 806, in FIG. 8) for carrying out any of the methods; a non-transitory computer-readable storage medium (e.g., memory 806, FIG. 8) comprising instructions stored thereon that, when executed by at least one processor (processor 804, FIG. 8), are configured to cause a computing system (e.g., 800, FIG. 8) to perform any of the example methods; and an apparatus (e.g., 800, FIG. 8) including at least one processor (e.g., processor 804, FIG. 8), and at least one memory (e.g., memory 806, FIG. 8) including computer program code, the at least one memory (806) and the computer program code configured to, with the at least one processor (804), cause the apparatus (e.g., 800) at least to perform any of the example methods.

[0274] Further embodiments of the present disclosure include the following examples.

[0275] Example 1.1. A user equipment (UE), comprising:means for receiving, by a user equipment (UE) from a source network node providing a source cell, a broadcast signal including an early timing advance (eTA) configuration for a neighboring cell, wherein the eTA configuration includes an indication of an eTA threshold and a contention-based random access (CBRA) resource associated with the neighboring cell, and wherein the CBRA resource includes PRACH information including at least one of a preamble, a RACH occasion, or a RACH frame timing;means for measuring, by the UE, at least one of a reference signal received power (RSRP) of a reference signal of the neighboring cell, a priority of the neighboring cell, or a number of the neighboring cell to perform eTA; andmeans for transmitting a random access request towards the neighboring cell using the CBRA resource, in response to determining the measured RSRP being above the eTA threshold.

[0276] Example 1.2. The UE of Example 1.1, wherein the eTA configuration is a cellspecific configuration and includes a cell-specific eTA configuration for the neighboring cell and a separate cell-specific eTA configuration for a further neighboring cell, and wherein at least one of the indicated eTA threshold or the CBRA resource are different from cell to cell.

[0277] Example 1.3. The UE of Examples 1.1 or 1.2, further comprising:means for transmitting, from the UE to the source network node, a message including a measurement report related to the neighboring cell, and an indication that an eTA request has been sent to the neighboring cell.

[0278] Example 1.4. The UE of any of Examples 1.1 to 1.3, wherein the measuring by the UE is performed after an eTA requirement report timer is started by the UE.

[0279] Example 1.5. The UE of any of Examples 1.1 to 1.4, further comprising:means for transmitting, by the UE, a CBRA based early timing advance (TA) request to the neighboring cell.

[0280] Example 1.6. The UE of any of Examples 1.1 to 1.5, further comprising:means for receiving, by the UE from the source network node, a command to access the neighboring cell and an associated neighboring cell timing advance (TA) value; andmeans for performing a RACH-less access to the neighboring cell based on the received TA value.

[0281] Example 1.7. The UE of any of Examples 1.1 to 1.6, further comprising:means for using, by the UE, CBRA RACH configuration information; andmeans for transmitting, by the UE, an early TA request to the neighboring cell.

[0282] Example 1.8. The UE of any of Examples 1.1 to 1.7, wherein when the UE is measuring at least one of the neighboring cell, a target cell, or a target network node, the UE is already in sync with at least one of the neighboring cell, the target cell, or the target network node.

[0283] Example 1.9. The UE of Example 1.8, wherein the UE can utilize an in-sync state to send an early TA request to the neighboring cell.

[0284] Example 1.10. The UE of any of Examples 1.1 to 1.9, further comprising:means for transmitting, by the UE to the source network node, PRACH information with a measurement report for the neighboring cell, wherein the source network node is configured to perform an enhanced handover decision based on the UE transmission, and wherein the source network node prioritizes at least one of the neighboring cell, a target cell, or a target network node for handover preparations, based on the UE transmission.

[0285] Example 1.13. A source network node, comprising:means for transmitting, by a source network node providing a source cell to a user equipment (UE), a broadcast signal including an early timing advance (eTA) configuration for a neighboring cell, wherein the eTA configuration includes an indication of an eTA threshold and a contention-based random access (CBRA) resource associated with the neighboring cell, and wherein the CBRA resource includes PRACH information including at least one of a preamble, a RACH occasion, or a RACH frame timing; andmeans for receiving, by the source network node, a random access request towards the neighboring cell using the CBRA resource, in response to determining a measured reference signal received power (RSRP) being above the eTA threshold.

[0286] Example 1.14. The source network node of Example 1.13, further comprising: means for starting, by the source network node, an eTA requirement report timer, wherein the source network node is configured to expect the UE to report measurement results with the PRACH information used to send eTA RACH requirements prior to an expiry of the eTA requirement report timer.

[0287] Example 1.15. The source network node of Example 1.14, further comprising: means for receiving, by the source network node from the UE, a message indicating that an eTA request has been sent to the neighboring cell, wherein the message is included in the next measurement report to reduce signaling.

[0288] Example 1.16. The source network node of Example 1.15, further comprising: means for performing, by the source network node, an enhanced handover decision, the source network node prioritizing at least one of the neighboring cell, a target cell, or a target network node for handover preparations based on the UE reporting the PRACH information with a measurement report for the neighboring cell over another candidate cell for which the UE has not performed eTA, considering all other handover criteria are met.

[0289] Example 1.17. The source network node of Example 1.14, wherein the CBRA resource includes a cell-specific eTA threshold configured to enable the UE to evaluate the neighboring cell without any explicit signaling between the source network node and the UE.

[0290] Example 1.18. The source network node of Example 1.14, further comprising: means for receiving, by the source network node from the UE, measurement results including PRACH information based on expiration of the eTA requirement report timer.

[0291] Example 1.19. The source network node of any of Examples 1.13 to 1.18, further comprising:means for transmitting, by the source network node to the neighboring cell, a handover preparation request including PRACH information and legacy content, for handover preparation.

[0292] Example 2.1 A user equipment (UE), comprising:means for receiving, by the UE from a source network node providing a source cell, a radio resource control (RRC) message including a first early timing advance (eTA) configuration for a neighboring cell and a measurement configuration for a neighboring cell, wherein the first eTA configuration includes an indication of an eTA threshold and a contention-based random access (CBRA) resource associated with the neighboring cell, and wherein the CBRA resource includesPRACH information including at least one of a preamble, a RACH occasion, or a RACH frame timing;means for measuring, by the UE, at least one of a reference signal received power (RSRP) of a reference signal of the neighboring cell, a priority of the neighboring cell, or a number of the neighboring cell; andmeans for transmitting a random access request towards the neighboring cell using the CBRA resource of the first eTA configuration, in response to determining the measured RSRP being above the eTA threshold of the first eTA configuration.

[0293] Example 2.2. The UE of Example 2.1, wherein the first eTA configuration is a UE-specific configuration, and wherein at least one of a speed, class, location, or measurement reporting offset are different from UE to UE.

[0294] Example 2.3. The UE of Example 2.1 or 2.2, further comprising:means for receiving, by the UE from the source network node providing the source cell, a broadcast signal including a second eTA configuration specific to the UE.

[0295] Example 2.4 The UE of Example 2.3, wherein the second eTA configuration is a cell-specific configuration and includes a cell-specific eTA configuration for the neighboring cell and a separate cell-specific eTA configuration for a further neighboring cell, wherein at least one of the indicated eTA threshold or the CBRA resource are different from cell to cell.

[0296] Example 2.5 The UE of any of Examples 2.1 to 2.4, further comprising: means for transmitting, from the UE to the source network node, a message including a measurement report related to the neighboring cell, and an indication that an eTA request has been sent to the neighboring cell.

[0297] Example 2.6 The UE of any of Examples 2.1 to 2.5, further comprising: means for transmitting, by the UE, a CBRA based eTA request to the neighboring cell.

[0298] Example 2.7 The UE of any of Examples 2.1 to 2.6, wherein the UE is receiving from the source network node a command to access the neighboring cell and an associated neighboring cell timing advance (TA) value, and performing a RACH-less access to the neighboring cell based on the received TA value.

[0299] Example 2.8 The UE of any of Examples 2.1 to 2.7, further comprising: means for using, by the UE, CBRA RACH configuration information; andmeans for transmitting, by the UE an early TA request to the neighboring cell.

[0300] Example 2.9 The UE of any of Examples 2.1 to 2.7, wherein when the UE is performing the measurement of the at least one neighboring cell, target cell, or the target network node, the UE is already in sync with the at least one neighboring cell, target cell, or target network node.

[0301] Example 2.10 The UE of Example 2.9, wherein the UE can utilize this in-sync state to send early TA request to the neighboring cell.

[0302] Example 2.13 A source network node, comprising:means for transmitting, by a source network node providing a source cell to a user equipment (UE), a radio resource control (RRC) message including a first early timing advance (eTA) configuration for a neighboring cell and a measurement configuration for a neighboring cell, wherein the first eTA configuration includes an indication of an eTA threshold and a contention-based random access (CBRA) resource associated with the neighboring cell, and wherein the CBRA resource includes PRACH information including at least one of a preamble, a RACH occasion, or a RACH frame timing; andmeans for receiving, by the source network node, a random access request towards the neighboring cell using the CBRA resource, in response to determining a measured reference signal received power (RSRP) being above the eTA threshold.

[0303] Example 2.14 The source network node of Example 2.13, wherein the first eTA configuration is a UE-specific configuration, wherein at least one of a speed, class, location, or measurement reporting offset are different from UE to UE.

[0304] Example 2.15 The source network node of Example 2.13 or 2.14, further comprising:means for transmitting, by the source network node providing the source cell to the UE, a broadcast signal including a second eTA configuration specific to the UE.

[0305] Example 2.16 The source network node of Example 2.15, wherein the second eTA configuration is a cell-specific configuration and includes a cell-specific eTA configuration for the neighboring cell and a separate cell-specific eTA configuration for a further neighboring cell, wherein at least one of the indicated eTA threshold or the CBRA resource are different from cell to cell.

[0306] Example 2.17 The source network node of Example 2.14, further comprising:means for receiving, by the source network node from the UE, a message indicating that an eTA request has been sent to the neighboring cell, wherein the message is included in the next measurement report to reduce signaling.

[0307] Example 2.18 The source network node of any of Examples 2.13 to 2.18, further comprising:means for transmitting, by the source network node, a handover preparation request including PRACH information and legacy content, to the neighboring cell, for handover preparation.

[0308] Example 2.19 The source network node of Example 2.18, further comprising:means for recognizing, by the source network node, an incoming handover preparation request;means for associating the source network node with the PRACH information; and means for transmitting, by the source network node to the UE, a stored timing advance (TA) in a handover command message piggybacked in a handover request acknowledgement.

[0309] Example 3.1 A user equipment (UE), comprising:means for transmitting, from a UE to a source network node providing a source cell, a message including a measurement report related to a neighboring cell;means for receiving, by the UE from the source network node providing the source cell, a physical downlink control channel (PDCCH) order to send an early timing advance (eTA) request to the neighboring cell, wherein the PDCCH order includes at least one of a priority of the neighboring cell or a number of the neighboring cell; and

[0310] transmitting, by the UE, a contention-based random access (CBRA) eTA request to the neighboring cell.

[0311] Example 3.2 The UE of Example 3.1, further comprising:means for receiving, by the UE from the source network node providing a source cell, a radio resource control (RRC) message including a first early timing advance (eTA) configuration and a measurement configuration for a neighboring cell, wherein the first eTA configuration includes an indication of an eTA threshold and a contention-based random access (CBRA) resource associated with the neighboring cell, and wherein the CBRA resource includes PRACH information including at least one of a preamble, a RACH occasion, or a RACH frame timing.

[0312] Example 3.3 The UE of Example 3.1 or 3.2, wherein the neighboring cell recognizes the CBRA eTA request based on the preamble of the PRACH information.

[0313] Example 3.4 The UE of any of Examples 3.1 to 3.3, wherein the first eTA configuration is a UE-specific configuration, wherein at least one of a speed, class, location, or measurement reporting offset are different from UE to UE.

[0314] Example 3.5 The UE of Example 3.2, further comprising:means for receiving, by the UE from the source network node providing a source cell, a broadcast signal including a second eTA configuration for the neighboring cell.

[0315] Example 3.6 The UE of Example 3.5, wherein the second eTA configuration is a cell-specific configuration and includes a cell-specific eTA configuration for the neighboring cell and a separate cell-specific eTA configuration for a further neighboring cell, wherein at least one of the indicated eTA threshold or the CBRA resource are different from cell to cell.

[0316] Example 3.7 The UE of any of Examples 3.1 to 3.6, further comprising:means for transmitting, from the UE to the source network node, an indication that an eTA request has been sent to the neighboring cell.

[0317] Example 3.8 The UE of any of Examples 3.1 to 3.7, wherein the UE is receiving from the source network node a command to access the neighboring cell and an associated neighboring cell timing advance (TA) value, and performing a RACH-less access to the neighboring cell based on the received TA value.

[0318] Example 3.9 The UE of any of Examples 3.1 to 3.8, further comprising:means for using, by the UE, CBRA RACH configuration information; andmeans for transmitting, by the UE an early TA request to the neighboring cell.

[0319] Example 3.10 The UE of any of Examples 3.1 to 3.9, wherein when the UE is performing the measurement of the at least one neighboring cell, target cell, or the target network node, and the UE is already in sync with the at least one neighboring cell, target cell, or target network node.

[0320] Example 3.13 A source network node, comprising:means for receiving, by a source network node providing a source cell, a message including a measurement report related to a neighboring cell;means for determining, by the source network node providing the source cell, that a measured reference signal received power (RSRP) is above an eTA threshold based on the measurement report; andmeans for transmitting, by the source network node providing the source cell to a user equipment (UE), a physical downlink control channel (PDCCH) order to send an early timing advance (eTA) request to the neighboring cell, wherein the PDCCH order includes at least one of a priority of the neighboring cell or a number of the neighboring cell.

[0321] Example 3.14 The source network node of Example 3.13, further comprising: means for transmitting, by the source network node providing the source cell to the UE, a radio resource control (RRC) message including a first eTA configuration and a measurement configuration for a neighboring cell, wherein the first eTA configuration includes an indication of the eTA threshold and a contention-based random access (CBRA) resource associated with the neighboring cell, wherein the CBRA resource includes PRACH information including at least one of a preamble, a RACH occasion, or a RACH frame timing.

[0322] Example 3.15 The source network node of Example 3.13 or 3.14, wherein the first eTA configuration is a UE-specific configuration, and wherein at least one of a speed, class, location, or measurement reporting offset are different from UE to UE.

[0323] Example 3.16 The source network node of any of Examples 3.13 to 3.15, further comprising:means for transmitting, by the source network node providing the source cell to the UE, a broadcast signal including a second eTA configuration specific to the UE for the neighboring cell, and wherein the second eTA configuration is a UE-specific configuration.

[0324] Example 3.17 The source network node of Example 3.16, wherein the second eTA configuration is a cell-specific configuration and includes a cell-specific eTA configuration for the neighboring cell and a separate cell-specific eTA configuration for a further neighboring cell, wherein at least one of the indicated eTA threshold or the CBRA resource are different from cell to cell.

[0325] Example 3.18 The source network node of Example 3.14, further comprising: means for receiving, by the source network node from the UE, a message indicating that an eTA request has been sent to the neighboring cell, wherein the message is included in the next measurement report to reduce signaling.

[0326] Example 3.19 The source network node of any of Examples 3.13 to 3.18, further comprising:means for transmitting, by the source network node, a handover preparation request including PRACH information and legacy content, to the neighboring cell, for handover preparation.

[0327] Example 3.20 The source network node of Example 3.18, further comprising: means for recognizing, by the source network node, an incoming handover preparation request;means for associating the UE with the PRACH information; andmeans for transmitting, by the source network node to the UE, a stored timing advance (TA) in a handover command message piggybacked in a handover request acknowledgement.

[0328] Example 4.1 A user equipment (UE), comprising:means for receiving, by a first UE from a source network node providing a source cell, a broadcast signal including an early timing advance (eTA) configuration for a neighboring cell, wherein the eTA configuration includes an indication of an eTA threshold, a contention-based random access (CBRA) resource associated with the neighboring cell, a preamble, a priority of a target network node, and a number of nodes to perform eTA associated with the neighboring cell;means for measuring, by the first UE, a reference signal received power (RSRP) of a reference signal of the neighboring cell; andmeans for transmitting, by the first UE to the source network node, a measurement report including PRACH information, wherein the PRACH information includes a preamble, a RACH occasion, and a RACH frame timing, wherein the PRACH information is the same as a second UE within a predetermined time period.

[0329] Example 4.2 The UE of Example 4.1, further comprising:means for receiving, by the first UE from the source network node, a CBRA based PDCCH order to retry for eTA acquisition based on contention.

[0330] Example 4.3 The UE of Example 4.1 or 4.2, further comprising:means for transmitting, from the first UE to the source network node, a message including a measurement report with PRACH info related to the neighboring cell, an indication that an eTA request has been sent to the neighboring cell, and the CBRA resource with the neighboring cell.

[0331] Example 4.4 The UE of any of Examples 4.1 to 4.3, further comprising:means for performing, by the first UE, a CFRA based eTA request with the neighboring cell.

[0332] Example 4.5 The UE of any of Examples 4.1 to 4.4, further comprising:means for receiving, by the first UE from the source network node, a handover command with timing advance, wherein the handover command includes a message indicating to fallback to RACH based handover.

[0333] Example 4.6 The UE of any of Examples 4.1 to 4.5, wherein the measuring by the UE is performed after an eTA requirement report timer is started by the UE.

[0334] Example 4.7 The UE of any of Examples 4.1 to 4.6, wherein the PDCCH order is received by the first UE and the second UE in a time staggered manner.

[0335] Example 4.10 A source network node, comprising:means for transmitting, by a source network node to a first user equipment (UE) and to a second UE, a broadcast signal including an early timing advance (eTA) configuration for a neighboring cell, wherein the eTA configuration includes an indication of an eTA threshold, a contention-based random access (CBRA) resource associated with the neighboring cell, a preamble, a priority of a target network node, and a number of nodes to perform eTA associated with the neighboring cell; andmeans for receiving, by the source network node, a measurement report including PRACH information, wherein the PRACH information includes a preamble, a RACH occasion, and a RACH frame timing, wherein the PRACH information is the same as the second UE within a predetermined time period.

[0336] Example 4.11 The source network node of Example 4.10, further comprising: means for starting, by the source network node, an eTA requirement report timer, wherein the source network node is configured to expect the first UE and the second UE to report measurement results with PRACH information used to send eTA RACH requirements prior to an expiry of the eTA requirement report timer.

[0337] Example 4.12 The source network node of Example 4.10 or 4.11, further comprising:means for receiving, by the source network node from each of the first UE and the second UE, a message indicating that an eTA request has been sent to the neighboring cell with the same PRACH information within an eTA requirement reporting time period.

[0338] Example 4.13 The source network node of Example 4.12, further comprising: means for detecting, by the source network node, a contention for CBRA based eTA acquisition request within a period of the eTA requirement report timer.

[0339] Example 4.14 The source network node of Example 4.13, further comprising:

[0340] transmitting, by the source network node to each of the first and second UE, a PDCCH order to retry for CBRA based or CFRA based eTA acquisition because of the detected contention.

[0341] Example 4.15 The source network node of Example 4.14, wherein the source network node further provides a RACH type to perform early timing advance acquisition, wherein a criteria for providing the RACH type includes a speed of each of the first and second UE, a DI and U1 RF condition, and a service type to which each of the first and second UE is subscribed.

[0342] Example 4.16 The source network node of Example 4.15, further comprising: means for determining, by the source network node, a handover decision; and means for transmitting, by the source network node to each of the first and second UE, a PDCCH order with PRACH resource for CFRA based eTA for the neighbor cell.

[0343] Example 4.17 The source network node of Example 4.12, further comprising: means for transmitting, by the source network node, a handover preparation request for the first and second UE, the handover preparation request including PRACH information and legacy content, to the neighboring cell, for handover preparation.

[0344] Example 4.18 The source network node of Example 4.17, further comprising: means for transmitting, by the source network node to the neighboring cell, PRACH information and a contention detected flag to target in a handover request message.

[0345] Example 4.19 The source network node of Example 4.18, further comprising: means for transmitting, by the source network node to the neighboring cell, a handover request message after an expiration of an eTA requirement report timer or after the measurement report is received and a handover decision is made.

[0346] Example 4.20 The source network node of Example 4.19, further comprising: means for transmitting, by the source network node to the neighboring cell, a handover request message with the PRACH information received in the measurement report.

[0347] Example 4.21 The source network node of Example 4.19, further comprising: means for transmitting, by the source network node to the neighboring cell, a handover request message and a contention detected flag, in a case where the source network node receivesanother measurement report with same PRACH information within a time period of the eTA request report.

[0348] Example 4.22 The source network node of Example 4.19, further comprising: means for transmitting, by the source network node, a handover preparation request for the first UE, the handover preparation request including PRACH information and legacy content, to the neighboring cell, for handover preparation.

[0349] Example 5.1 A user equipment (UE), comprising:means for receiving by a first UE from a source network node, a broadcast signal including an early timing advance (eTA) configuration for a neighboring cell, wherein the eTA configuration includes an indication of an eTA threshold, a contention-based random access (CBRA) resource associated with the neighboring cell, a preamble, a priority of a target network node, and a number of nodes to perform eTA;means for measuring, by the first UE, a reference signal received power (RSRP) of a reference signal of the neighboring cell; andmeans for transmitting, by the first UE to the target network node, a CBRA based RACH request for eTA acquisition prior to the target network node starting an eTA requirement report timer, wherein the target network node is configured to expect the first UE and a second UE to report measurement results with PRACH information used to send eTA RACH requirements prior to an expiry of the eTA requirement report timer.

[0350] Example 5.2 The UE of Example 5.1, further comprising:means for determining, by the first UE, that a handover command is not received from the target network node within a time period.

[0351] Example 5.3 The UE of Example 5.2, wherein the determination includes determining that a retry value is less than an eTA RACH counter value.

[0352] Example 5.4 The UE of any of Examples 5.1 to 5.4, further comprising:means for transmitting, by the first UE to the target network node, a CBRA based RACH request to retry for eTA acquisition based on contention.

[0353] Example 5.5 The UE of any of Examples 5.1 to 5.4, further comprising:means for transmitting, from the UE to the source network node, a message including a measurement report with PRACH information related to the neighboring cell, an indication thatan eTA request has been sent to the neighboring cell, and the CBRA resource with the neighboring cell.

[0354] Example 5.6 The UE of any of Examples 5.1 to 5.5, further comprising:means for receiving, by the first UE from the source network node, a handover command with timing advance, wherein the handover command includes a message indicating to fallback to RACH based handover.

[0355] Example 5.7 The UE of any of Examples 5.1 to 5.6, further comprising:means for receiving, by the first UE from the source network node, an RRC reconfiguration indicating to fallback to CFRA based eTA acquisition.

[0356] Example 5.10 A target network node, comprising:means for receiving, by a target network node from a first UE, a CBRA based RACH request for eTA acquisition prior to the target network node starting an eTA requirement report timer, wherein the target network node is configured to expect the first UE and a second UE to report, to a source network node serving a source cell, measurement results with PRACH information used to send eTA RACH requirements prior to an expiry of the eTA requirement report timer to enable the source network node to send a handover request to the target network node;means for receiving, by the target network node for each of the first UE and a second UE, within a predetermined time period, a handover request message from a source network node including PRACH information, the PRACH information including a preamble, a RACH occasion, a RAC frame, and timing, wherein the PRACH information from the first UE is the same as the PRACH information from the second UE; andmeans for detecting, by the target network node, a contention caused by the first UE and the second UE.

[0357] Example 5.11 The target network node of Example 5.10, further comprising: means for starting, by the target network node, an eTA requirement report timer.

[0358] Example 5.12 The target network node of Example 5.11, further comprising: means for receiving, by the target network node from the second UE, a CBRA based RACH request for eTA acquisition after the target network node starts the eTA requirement report timer.

[0359] Example 5.13 The target network node of any of Examples 5.10 to 5.12, further comprising:means for receiving, by the target network node from the first UE, a CBRA based RACH request to retry for eTA acquisition based on the contention.

[0360] Example 5.14 The target network node of any of Examples 5.10 to 5.13, further comprising:means for transmitting, by the target network node to a source network node, a handover request message including a message indicating to fallback to RACH based handover.

[0361] Example 5.15 The target network node of any of Examples 5.10 to 5.14, further comprising:means for transmitting, by the target network node to a source network node, an RRC reconfiguration indicating to fallback to CFRA based eTA acquisition.

[0362] Example 5.16 The target network node of any of Examples 5.10 to 5.15, further comprising:means for transmitting, by the target network node to a source network node, a handover request message including PRACH information and legacy content for handover preparation.

[0363] Example 5.17 The target network node of any of Examples 5.10 to 5.16, further comprising:means for receiving, by the target network node from the first UE, a timing advance preamble to trigger eTA acquisition.

[0364] Example 5.18 The target network node of Example 5.17, further comprising: means for transmitting, by the target network node to a source network node, an RRC configuration message for the first UE and the second UE for RRC reconfiguration preparation.

[0365] The embodiments and aspects disclosed herein are examples of the present disclosure and may be embodied in various forms. For instance, although certain embodiments herein are described as separate embodiments, each of the embodiments herein may be combined with one or more of the other embodiments herein. Specific structural and functional details disclosed herein are not to be interpreted as limiting, but as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the present disclosure in virtually any appropriately detailed structure. Like reference numerals may refer to similar or identical elements throughout the description of the figures.

[0366] The phrases “in an aspect,” “in aspects,” “in various aspects,” “in some aspects,” or “in other aspects” may each refer to one or more of the same or different aspects in accordance with this present disclosure. The phrase “a plurality of’ may refer to two or more.

[0367] In various embodiments, the terms “first message” and “second message,” as well as any subsequent messages may refer to any messages that are transmitted or received in an order and are not necessarily limited to any particular message.

[0368] The phrases “in an embodiment,” “in embodiments,” “in various embodiments,” “in some embodiments,” or “in other embodiments” may each refer to one or more of the same or different embodiments in accordance with the present disclosure. A phrase in the form “A or B” means “(A), (B), or (A and B).” A phrase in the form “at least one of A, B, or C” means “(A); (B); (C); (A and B); (A and C); (B and C); or (A, B, and C) ”

[0369] Any of the herein described methods, programs, algorithms or codes may be converted to, or expressed in, a programming language or computer program. The terms “programming language” and “computer program,” as used herein, each include any language used to specify instructions to a computer, and include (but is not limited to) the following languages and their derivatives: Assembler, Basic, Batch files, BCPL, C, C+, C++, Delphi, Fortran, Java, JavaScript, machine code, operating system command languages, Pascal, Perl, PL1, Python, scripting languages, Visual Basic, metalanguages which themselves specify programs, and all first, second, third, fourth, fifth, or further generation computer languages. Also included are database and other data schemas, and any other meta- languages. No distinction is made between languages which are interpreted, compiled, or use both compiled and interpreted approaches. No distinction is made between compiled and source versions of a program. Thus, reference to a program, where the programming language could exist in more than one state (such as source, compiled, object, or linked) is a reference to any and all such states. Reference to a program may encompass the actual instructions and / or the intent of those instructions.

[0370] While aspects of the present disclosure have been shown in the drawings, it is not intended that the present disclosure be limited thereto, as it is intended that the present disclosure be as broad in scope as the art will allow and that the specification be read likewise. Therefore, the above description should not be construed as limiting, but merely as exemplifications of particular aspects. Those skilled in the art will envision other modifications within the scope and spirit of the claims appended hereto.

Claims

WE CLAIM:

1. A method, comprising:receiving by a first user equipment (UE) from a source network node, a broadcast signal including an early timing advance (eTA) configuration for a neighboring cell, wherein the eTA configuration includes an indication of an eTA threshold, a contention-based random access (CBRA) resource associated with the neighboring cell, a preamble, a priority of a target network node, and a number of nodes to perform eTA;measuring, by the first UE, a reference signal received power (RSRP) of a reference signal of the neighboring cell; andtransmitting, by the first UE to the target network node, a CBRA based RACH request for eTA acquisition prior to the target network node starting an eTA requirement report timer, wherein the target network node is configured to expect the first UE and a second UE to report measurement results with PRACH information used to send eTA RACH requirements prior to an expiry of the eTA requirement report timer.

2. The method of claim 1, further comprising:determining, by the first UE, that a handover command is not received from the target network node within a time period.

3. The method of claim 2, wherein the determination includes determining that a retry value is less than an eTA RACH counter value.

4. The method of claim 1, further comprising:transmitting, by the first UE to the target network node, a CBRA based RACH request to retry for eTA acquisition based on contention.

5. The method of claim 1, further comprising:transmitting, from the UE to the source network node, a message including a measurement report with PRACH information related to the neighboring cell, an indication that57an eTA request has been sent to the neighboring cell, and the CBRA resource with the neighboring cell.

6. The method of claim 1, further comprising:receiving, by the first UE from the source network node, a handover command with timing advance, wherein the handover command includes a message indicating to fallback to RACH based handover.

7. The method of claim 1, further comprising:receiving, by the first UE from the source network node, an RRC reconfiguration indicating to fallback to CFRA based eTA acquisition.

8. A user equipment (UE) , comprising:at least one processor; andat least one memory storing instructions which, when executed by the at least one processor, cause the UE at least to perform a method as in any one of claims 1 to 7.

9. A method, comprising:receiving, by a target network node from a first UE, a CBRA based RACH request for eTA acquisition prior to the target network node starting an eTA requirement report timer, wherein the target network node is configured to expect the first UE and a second UE to report, to a source network node serving a source cell, measurement results with PRACH information used to send eTA RACH requirements prior to an expiry of the eTA requirement report timer to enable the source network node to send a handover request to the target network node;receiving, by the target network node for each of the first UE and a second UE, within a predetermined time period, a handover request message from a source network node including PRACH information, the PRACH information including a preamble, a RACH occasion, a RAC frame, and timing, wherein the PRACH information from the first UE is the same as the PRACH information from the second UE; anddetecting, by the target network node, a contention caused by the first UE and the second UE.

10. The method of claim 9, further comprising:starting, by the target network node, an eTA requirement report timer.

11. The method of claim 10, further comprising:receiving, by the target network node from the second UE, a CBRA based RACH request for eTA acquisition after the target network node starts the eTA requirement report timer.

12. The method of claim 10, further comprising:receiving, by the target network node from the first UE, a CBRA based RACH request to retry for eTA acquisition based on the contention.

13. The method of claim 10, further comprising:transmitting, by the target network node to a source network node, a handover request message including a message indicating to fallback to RACH based handover.

14. The method of claim 9, further comprising:receiving, by the target network node from the first UE, a timing advance preamble to trigger eTA acquisition.

15. A processor-readable medium storing instructions which, when executed by at least one processor of a network apparatus, cause the network apparatus at least to perform a method as in any one of claims 9 to 14.

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