A terminal apparatus applies, in a case that a handover command is received, and the handover command includes skip information (rach-Skip) for indicating that a random access procedure for a target primary cell is skipped, a value of N.sub.TA indicated by target TA information (targetTA) included in the skip information (rach-Skip) to a target primary Timing Advance Group (TAG) after synchronization with a downlink of the target primary cell is initiated, and starts a Time Alignment (TA) timer associated with the target primary TAG.

A method and apparatus are disclosed. In an example from the perspective of a User Equipment (UE), a signal to configure the UE to perform a Random Access Channel-less (RACH-less) handover to a second cell may be received in a first cell, wherein the signal comprises a candidate list of beams for Physical Downlink Control Channel (PDCCH) monitoring in the second cell and/or the signal is indicative of a first beam of the candidate list of beams (to be used by the UE for PDCCH monitoring). A PDCCH in the second cell on the first beam may be monitored before receiving a Medium Access Control (MAC) Control Element (CE) assigning a second beam for PDCCH monitoring in the second cell.

A method by a user equipment in a wireless communication system includes receiving an access command from a source node, the access command instructing the UE to access a target cell and including an access configuration specifying an access method without random access and one or more valid target cell beams for which the access configuration is valid at the target cell, and accessing the target cell in response to the access command.

A wireless device receives, from a base station, configuration parameters indicating power control parameters and downlink reference signals. The wireless device selects a power control parameter, from the power control parameters, associated with a downlink reference signal with a highest radio link quality of the downlink reference signals. The wireless device transmits, with an uplink transmission power determined based on the power control parameter, an uplink transport block via a physical uplink shared channel (PUSCH).

An example technique is provided for receiving, by a target base station (BS) from a source PS, information identifying a source cell or the source BS, and a first time advance value used by the user device to transmit signals to the source BS, receiving a signal by the target BS that was transmitted from the user device based on the first tune advance value, determining, by the target BS based upon the first time advance value and the received signal from the user device, a second time advance value to be used by the user device to transmit data to the target BS, sending the second time advance value from the target BS to the source BS, receiving, by the target BS, a handover of the user device from the source BS to the target BS, and receiving data by the target BS from the user device based on the second time advance value.

The present disclosure relates to a communication method and system for converging a 5th-Generation (5G) communication system for supporting higher data rates beyond a 4th-Generation (4G) system with a technology for Internet of Things (IoT). The present disclosure may be applied to intelligent services based on 5G communication technology and IoT-related technology, such as smart home, smart building, smart city, smart car, connected car, health care, digital education, smart retail, security and safety services. A handover method of a terminal in a mobile communication system according to the present disclosure includes transmitting UE capability information including a random access-free handover indicator to a first base station, receiving a handover command message from the first base station, and transmitting, when the handover command message includes uplink resource information, a handover complete message to a second base station based on the uplink resource information.

A method for receiving a radio resource control (RRC) message by a user equipment (UE) is described. The method includes receiving, from a base station, an RRC connection reconfiguration message for adding a secondary cell group (SCG), wherein the RRC connection reconfiguration message includes data radio bearer (DRB) configuration parameters for remapping a DRB that is established on a master cell group (MCG), to the SCG; and remapping the DRB to the SCG based on the RRC connection reconfiguration message, wherein the DRB configuration parameters include a packet data convergence protocol (PDCP) configuration.

In general, the current subject matter relates to prioritizing random access channel layer-less (RACH-less) layer 1/layer 2 triggered mobility (LTM). In some implementations, prioritizing RACH-less LTM can include receiving, at a serving distributed unit (DU) of a base station from a centralized unit control plane of the base station, information indicative of a RACH-less handover configuration for a plurality of LTM target cells of the base station or timing advance information for each of the plurality of LTM target cells; identifying, at the serving DU and based on the received information, at least one of the target cells for which RACH-less handover of service for a user equipment (UE) can be performed; and selecting, at the serving DU, one of the at least one identified target cells for handover of service for the UE from the serving DU, and triggering the handover of the service to the selected target cell.

In general, the current subject matter relates to realizing random access channel layer-less (RACH-less) layer 1/layer 2 triggered mobility (LTM). In some implementations, realizing RACH-less LTM can include receiving, at at least one LTM target cell of a base station, information indicative of whether handover (HO) of service for a user equipment (UE) currently being served by a serving DU of the base station can be a random access channel-less (RACH-less) HO to the at least one target cell or can be a RACH-based HO to the at least one target cell, and preparing the at least one LTM target cell, based on the information received at the at least one LTM target cell, for one of RACH-less HO and RACH-based HO.

A method (400) in a radio network node (220) of a wireless communication system (200) for selecting a MSG3 size for a User Equipment (UE) (230) that is performing handover from a serving network node (210) to a neighbor network node (220) is disclosed. The method (400) comprises receiving (S402) 5 measurement information related to the UE (230) from the serving network node (210). The method (400) comprises selecting (S404) the MSG3 size based on the measurement information. The method (400) further comprises transmitting (S406) the MSG3 size to the UE (230), based on which UE related information is transmitted to the neighbor network node (220).