A communication device for RNTI allocation comprises a processing means, for executing a program, and a storage unit, coupled to the processing means, for storing the program which instructs the processing means to perform the steps: connecting to a first base station, receiving a first RNTI assigned by the first base station, receiving a RRC message including a second RNTI for communication with a second base station from the first base station, transmitting a RRC message response to the first base station, performing communication with the first base station with the first RNTI and communication with the second base station with the second RNTI, transmitting a random access preamble to the second base station, receiving a random access response from the second base station, transmitting a scheduled transmission containing the second RNTI to the second base station, and receiving a contention resolution message from the second base station.

A random access method comprises: transmitting, by a firstuser equipment (UE) in a UE group, and according to a time-frequency resource, a preamble to an evolved node B (eNB); and monitoring, by a second UE in the UE group and/or the first UE, for a random access response (RAR) corresponding to the preamble transmitted by the eNB, wherein the first UE is at least one UE in the UE group, and the second UE is all or a part of the UEs in the UE group.

One embodiment of the present specification provides a method for performing a random access procedure. The method can comprise the steps of: generating a random access preamble to a first cell; generating a random access preamble to a second cell; determining whether the random access preamble to the first cell and the random access preamble to the second cell are triggered so as to be simultaneously transmitted in the same subframe; selecting the random access preamble to any one of the cells according to a pre-set priority when triggered so as to be simultaneously transmitted; and transmitting the any one selected random access preamble.

A method for perform pre-processing for handover of a moving cell by a serving base station, the method comprises transmitting a handover pre-processing request message including information on a handover history of the moving cell, to at least one neighboring base station adjacent to the serving base station; receiving a pre-processing response message including at least one of a random access preamble allocated from the neighboring base station, radio resource control (RRC) configuration of the neighboring base station and system information of the neighboring base station, from the neighboring base station; and transmitting the pre-processing response message to the moving cell before handover of the moving cell is initiated.

A target communications device receiving from a source communications device a notification that a user communications device is to be handed over from that source communications device, provides the source communications device with multiple component carrier information for use by the user communications device. The multiple component carrier information includes information indicating to the user communications device which of the multiple component carriers is to be used for initial access. The multiple component carrier information may be component carrier indexes. Communication devices may exchange component carrier indexes during a setup or updating procedure such as an X2 setup or updating procedure.

The present invention discloses a base station, a terminal, and a handover method. The handover method includes: sending an indication message by a base station, wherein the indication message is used to instruct the terminal to further establish a connection to the base station through a second channel in a case in which the terminal maintains a connection to the base station through a first channel; receiving an access message by the base station through the first channel, wherein the access message indicates that the terminal has established the connection to the base station through the second channel; sending a handover command by the base station, wherein the handover command instructs the terminal to switch the communication with the base station from the first channel to the second channel; and switching, by the base station, communication with the terminal from the first channel to the second channel.

The present document discloses a method for transmitting/receiving signals using direct device-to-device (D2D) communication by using similar random access procedures in a wireless communication system, and a device therefor. To this end, one aspect of the present invention provides a method whereby a base station supports the device-to-device (D2D) communication of a terminal in idle mode in a wireless communication system, the base station according to the method: receiving a first message, which corresponds to one among a predetermined number of signatures for D2D communication, from a D2D transmission terminal; and transmitting a second message, which comprises control information for D2D signal reception, to one or more D2D reception terminals including a terminal in idle mode, wherein the second message allows the terminal in idle mode to receive a third message comprising a D2D broadcast or groupcast signal transmitted by the D2D transmission terminal.

Embodiments provide a data transmission method, a device, and a system. The method includes: acquiring, by user equipment, a first preamble corresponding to a cell set of a primary timing advance group of a first base station and a second preamble corresponding to a cell set of a secondary timing advance group of a second base station; sending the first preamble to the first base station, to initiate random access to the first base station according to the first preamble; and sending the second preamble to the second base station, to initiate random access to the second base station according to the second preamble.

A method for supporting a secondary cell (SCell) addition in a radio access system that supports a carrier aggregation (CA), the method is performed by a primary cell (PCell) of a first timing advanced group (TAG) and includes acquiring, from a SCell of a second TAG, random access channel (RACH) resource information related to a random access procedure, wherein the random access procedure is to be performed at the SCell in order to add the SCell to the first TAG; transmitting, to a user equipment (UE), SCell related information, wherein the SCell related information includes a cell identifier of the SCell and the RACH resource information; and receiving, from the UE, a message reporting that the random access procedure at the SCell has failed, wherein the RACH resource information includes RACH parameters required to perform the random access procedure, and wherein a timing advanced value of the first TAG is different from a timing advanced value of the second TAG.

A method and apparatus for timing advance (TA) synchronization for uplink (UL) data transmissions are provided. A base station transmits a TA instruction to a UE. The TA instruction indicates one of at least two TA options. The first TA option indicates direct initial grant-free (GF) uplink (UL) data transmissions. The second TA option indicates indirect initial GF UL data transmissions with the UE initiating TA reference signaling for updating a TA parameter of the UE. The UE performs an initial GF UL data transmission to the base station based on the TA instruction.