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 performed by a terminal in a wireless communication system is provided. The method includes receiving, from a base station, a radio resource control (RRC) message including layer 1 (L1)/layer 2 (L2) triggered mobility (LTM) configuration information, the LTM configuration information including at least one LTM candidate configuration for at least one candidate cell, transmitting, to the base station, a report for an L1 measurement on the at least one candidate cell, receiving, from the base station via a medium access control (MAC) control element (CE), an LTM cell switch command based on the report, identifying whether a value of a timing advance command (TAC) in the MAC CE is set to a specific value, and in case that the value of the TAC is not set to the specific value, processing the TAC and performing a random access channel (RACH)-less LTM cell switch for a target cell identified by the MAC CE.

Methods, systems, and devices for wireless communications are described. The described techniques may provide for efficiently triggering a handover at a user equipment (UE) from a source cell to a target cell. The UE may receive, at a first time period, a first control message including a configuration of a target cell to use at a second time period for performing a handover procedure from a source cell to a target cell. The UE may then receive, at the second time period, a second control message triggering the UE to perform the handover procedure from the source cell to the target cell. The UE may use the configuration of the target cell received in the first control message to perform a handover procedure from the source cell to the target cell at the second time period in response to receiving the second control message.

A user equipment (UE) and a method of uplink beam management are provided. The method includes being configured, by a source cell, an uplink transmit beam for an uplink transmission for a target cell and transmitting, to the target cell, the configured uplink transmit beam for the uplink transmission. During a handover from the source cell to the target cell, the uplink transmit beam for the UE to the target cell is determined based on collaboration between the source cell and the target cell. The method enables a random access channel-free (RACH-free) handover procedure which reduces latency of handover and overhead of signaling and resource.

The disclosure relates to a 5G or 6G communication system for supporting a higher data transmission rate. According to one embodiment, a method for operating a user equipment (UE) in a wireless communication system may comprise receiving an L1/L2 triggered mobility (LTM) medium access control control element (MAC CE) from a base station, determining whether the LTM MAC CE includes a timing advance (TA) value or a random access channel (RACH)-less handover indicator, and when the LTM MAC CE includes the TA value or the RACH-less handover indicator, performing a handover procedure to a target cell based on the TA value or the RACH-less handover indicator.

A communication scheme and a system thereof are provided for converging IoT technology and a 5G communication system for supporting a high data transmission rate beyond that of a 4G system. The disclosure can be applied to intelligent services based on the 5G communication technology and the IoT-related technology. The disclosure provides a method of minimizing a handover delay and a handover failure possibility of the terminal in a mobile communication system, which includes receiving a handover command from a first BS; performing DL synchronization with a second BS; determining whether a first UL signal to be transmitted to the first BS and a second UL signal to be transmitted to the second BS overlap; and in response to determining that the first UL signal and the second UL signal overlap, transmitting the second UL signal to the second BS, wihtout transmitting the first UL signal to the first BS.

A method for receiving a radio resource control (RRC) message by a user equipment (UE) is described. The method includes receiving an RRC connection reconfiguration (RRCConnectionReconfiguration) message including secondary cell group (SCG) configuration parameters. The RRC connection reconfiguration message has a structure that the SCG configuration parameters do not include a data radio bearer (DRB) configuration.

Embodiments of Evolved Node-B (eNBs), user equipment (UE) and methods for licensed shared access (LSA) handover are generally described herein. An eNB includes hardware processing circuitry to receive a command to release spectrum resources in a LSA band over which the eNB serves an LSA cell; to determine whether user equipment (UEs) served by the eNB are permitted to skip a random access process (RAP) to be handed over to a target cell operating on a band separate from the LSA band; and to transmit a message to a UE served by the eNB instructing the UE that the UE is to be handed over to the target cell, the message including one or more indicators based on the determination. Other apparatuses, systems and methods are also disclosed.

A method for receiving a radio resource control (RRC) message by a user equipment (UE) is described. The method includes receiving an RRC connection reconfiguration (RRCConnectionReconfiguration) message including secondary cell group (SCG) configuration parameters. The RRC connection reconfiguration message has a structure that the SCG configuration parameters do not include a data radio bearer (DRB) configuration.

The present disclosure relates to a user equipment (UE) that comprises a receiver of the UE receives, from a source base station of a source radio cell, a common timing advance value for a target radio cell. The UE is connected to the source radio cell and is involved in a handover procedure to hand over the UE from the source radio cell to the target radio cell. Further, the common timing advance value is received from the source base station in a first message of the handover procedure, which also comprises a timing indication for transmitting a second message from the UE to the target base station. Then, a processor of the UE determines a first uplink timing of uplink transmissions to the target base station with respect to downlink transmissions from the target base station, based on the received common timing advance value and the timing indication. A transmitter of the UE transmits a second message of the handover procedure to the target base station based on the determined uplink timing. The processor determines a UE-specific timing advance value, specific to the UE and the target radio cell, to be used by the UE for performing uplink transmissions in the target radio cell.