A process allows a UE to acquire a System Frame Number (SFN) before accessing a target base station/node during a RACH-less handover. The SFN may be provided to the UE in various ways. For example, the SFN may be provided as part of a handover command message (e.g., RRCReconfiguration) or a master information block (MIB). In this manner, the UE acquires the SFN before accessing the target base station/node, which allows the target base station/node and the UE to effect certain timings for the handover. For example, the target base station/node and the UE may set time bounds in which the handover must occur. As another example, different types of uplink grants may be set.

Methods and apparatuses are provided in a wireless communication system. A radio link control (RLC) protocol data unit (PDU) is obtained from a lower layer. A status PDU is generated based on the RLC PDU. The status PDU includes a first field indicating a sequence number (SN) of an RLC data unit identified as lost, a second field indicating a number of consecutively lost RLC data units starting from and including the SN, and a third field indicating whether the second field follows the first first field. The status PDU is delivered to the lower layer.

A terminal apparatus includes a receiver configured to receive a radio resource control (RRC) reconfiguration message from a base station apparatus, and a controller configured to configure a parameter based on the parameter included in the RRC reconfiguration message. The parameter includes at least identity information of a target cell and a configuration of a subcarrier spacing, and the configuration of the subcarrier spacing is configured for each of the target cells.

A method and an apparatus for synchronized handover in a mobile communication system are provided. A source base station providing data to a terminal transmits a handover command message for handover to a target base station to the terminal, and interrupts transmission of data to the terminal when the source base station receives a message for informing a handover execution timing from the terminal later. In addition, the source base station forwards data on the terminal to the target base station.

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.

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 invention inter alia pertains to an apparatus for communication with a non-terrestrial network, NTN, the apparatus comprising means configured for: receiving, from the network, a handover configuration regarding a handover to be performed by the apparatus from a source cell to a target cell of the network; receiving, from the network, assistance information for the apparatus to connect to said target cell; determining, based on the assistance information, a type of the handover or receiving, from the network, an indication of a type of the handover; determining, based on the handover type, a threshold for a timing advance parameter; determining, based on the threshold and a value of the timing advance parameter, whether to perform a RACH-less handover towards the target cell.

This disclosure provides systems, methods, and apparatuses for low latency handover between secondary nodes (SNs). In one aspect, a user equipment (UE) may receive a configuration for a plurality of SNs, receive a command to communicate via an SN of the plurality of the SNs, and determine a handover procedure that is to be used to establish a connection with the SN. The handover procedure may be a random access channel (RACH)-less or a two-step RACH procedure and is determined to be used based on a determination that uplink time synchronization is established with the SN.

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.

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.