Abstract: An operation method of a terminal in a communication system may include: receiving, from a base station, primary RA configuration information for a primary RA procedure; receiving, from the base station, secondary RA configuration information for a secondary RA procedure; transmitting a primary RA preamble to the base station by using a primary RA resource indicated by the primary RA configuration information; receiving, from the base station, secondary RA indication information in response to the primary RA preamble, the secondary RA indication information indicating to perform the secondary RA procedure instead of the primary RA procedure; and transmitting a secondary RA preamble to the base station by using a secondary RA resource indicated by the secondary RA configuration information.

Abstract: An operation method of a first terminal may include: configuring a Uu access link with a base station, and receiving a first message from the base station, the first message including a relay RNTI for identifying the first terminal, a node address of the base station, and a RAP entity ID for identifying a RAP entity configured for the first terminal; configuring a relay link with a second terminal when communication with the base station is disconnected; requesting link switching by transmitting to the base station a second message via the second terminal, the second message including the relay RNTI, node address, and RAP entity ID; and receiving a response to the second message from the base station via the second terminal, and switching a link with the base station from the Uu access link to the relay link.

Abstract: An operation method of an IAB node in a communication system may comprise: measuring a power difference between a first signal received from a first node and a second signal received from a second node; controlling a transmit power of each of the first node and the second node based on the power difference; generating scheduling information for allowing the first node and the second node to simultaneously transmit signals; transmitting the scheduling information to the first node and the second node; and receiving signals that the first node and the second node simultaneously transmit according to the scheduling information by using the transmit power.

Abstract: An operation method of a first terminal in a communication system may comprise: receiving a link establishment request message from a second terminal; transmitting, to the second terminal, a link establishment response message including a node address of a first base station in response to the link establishment request message; and receiving a link establishment completion message from the second terminal.

Abstract: A method for performing sidelink groupcast transmission by a transmission terminal includes the steps of: classifying reception terminals belonging to a subject group into two or more subgroups; allocating different groupcast feedback schemes to the two or more subgroups; performing groupcast transmission to the reception terminals; and receiving feedback information from terminals belonging to at least one subgroup among the two or more subgroups according to the different groupcast feedback schemes.

Abstract: A sidelink communication method performed by a UE in a communication system may comprise receiving, from a base station, a message including configuration information of a subchannel which is a sensing unit of a resource pool; determining a size of the subchannel based on the configuration information; and performing a sensing operation in units of the subchannel in the resource pool. Therefore, the sidelink communication can be efficiently performed, and the performance of the communication system can be improved.

Abstract: An operation method of a terminal in a communication system includes receiving a message from a base station, the message including physical random access channel (PRACH) configuration information indicating a PRACH slot; determining a start symbol to which a PRACH is mapped among symbols constituting the PRACH slot based on a type of the PRACH slot; mapping the PRACH from the start symbol in the PRACH slot; and transmitting the PRACH mapped to the PRACH slot to the base station.

Abstract: An operation method of a first terminal, performed in a communication system, may comprise receiving sidelink resource allocation information from a base station; receiving a first sidelink signal from a second terminal based on the sidelink resource allocation information; calculating a path loss experienced by the first sidelink signal based on the first sidelink signal; transmitting a second sidelink signal including information on the path loss experienced by the first sidelink signal to the second terminal; and receiving, from the second terminal, a third sidelink signal to which a sidelink transmit power determined based on the path loss is allocated.

Abstract: A method for managing links, performed by a first communication node in a communication system, includes: obtaining, through an interface, communication status information including communication quality information for each link between the first communication node and at least one other communication node of the communication system; obtaining communication environment information including movement information and location information of each of the at least one other communication node; and obtaining a link probability computational model outputting a first link probability according to input of the communication status information by iteratively performing a machine learning operation based on the communication status information and the communication environment information, wherein the first link probability is used by the first communication node to control multi-connectivity with the at least one other communication node.

Abstract: An operation method of a first terminal, performed in a communication system, may comprise receiving sidelink resource allocation information from a base station; receiving a first sidelink signal from a second terminal based on the sidelink resource allocation information; calculating a path loss experienced by the first sidelink signal based on the first sidelink signal; transmitting a second sidelink signal including information on the path loss experienced by the first sidelink signal to the second terminal; and receiving, from the second terminal, a third sidelink signal to which a sidelink transmit power determined based on the path loss is allocated.

Abstract: A method for transmitting and receiving a message for a random access (RA) between user equipment (UE) and a base station in a multi beam system includes: transmitting a synchronization signal (SS) block including a synchronization signal by performing beam sweeping for a multi beam; receiving a message 1 of an RA procedure from the UE; determining an optimal transmission beam to be used to transmit a message 2 of the RA procedure based on information about an association mapping between the SS block and a physical random access channel (PRACH) which is used to transmit the message 1; and transmitting the message 2 by using the optimal transmission beam.

Abstract: A method and an apparatus for random access in a mobile communication system are provided. A terminal receives a synchronization signal block, obtains beam index information from the received synchronization signal block, and transmits a preamble message occupying a plurality of preamble resources including a preamble resource corresponding to the beam index information to a base station. A random access resource includes a plurality of preamble resources, and the synchronization signal block is specified for one beam and corresponds to one preamble resource of the random access resource.

Abstract: Provided are a method and a device for triggering a beam failure recovery (BFR) procedure of a multibeam system by means of the steps of: detecting a beam failure by monitoring a wireless link connected with a base station; identifying a candidate transmission beam of the base station; and transmitting a BFR request to the base station when the candidate transmission beam of the base station is identified.

Abstract: A method of performing, by a device, a random access procedure in a radio communication system includes: receiving from a base station RACH configuration information; and transmitting a first message based on the received RACH configuration information. Herein, a plurality of SSBs may be in association with a plurality of preambles, and the first message may be transmitted in a time domain through a plurality of RACH resources.

Abstract: A method for sidelink groupcast transmission, performed by a transmitting terminal, may comprise configuring a first feedback resource located at a first time point and a second feedback resource located at a later time point than the first time point; transmitting groupcast control information and groupcast data to a receiving terminal group; receiving first feedback information through the first feedback resource from at least one terminal belonging to a first subgroup of the receiving terminal group; and receiving second feedback information through the second feedback resource from at least one terminal belonging to a second subgroup of the receiving terminal group.

Abstract: A method and an apparatus for transmitting a message used to access a base station (BS) in a random access (RA) procedure by user equipment (UE) are provided. The method includes: determining a first RA preamble resource corresponding to an SSB index which corresponds to a transmission beam among a plurality of transmission beams of BS; and transmitting a message 1 of the RA procedure by using a first RA preamble format which includes the first RA preamble resource and at least one second RA preamble resource which neighbors the first RA preamble resource.

Abstract: A sidelink communication method performed by a UE in a communication system may comprise receiving, from a base station, a message including configuration information of a subchannel which is a sensing unit of a resource pool; determining a size of the subchannel based on the configuration information; and performing a sensing operation in units of the subchannel in the resource pool. Therefore, the sidelink communication can be efficiently performed, and the performance of the communication system can be improved.

Abstract: A high speed moving terminal including first and second antennas each communicating with first and second radio units (RUs) of a base station distributedly installed in a mobile wireless backhaul network communicates with the first and second RUs, respectively, with different uplink-downlink configuration of the first RU and the second RU, and transmits control information of the corresponding downlink signal in an uplink subframe that comes first in the time domain after processing latency of a downlink signal received from the first RU among uplink frames with the uplink-downlink configurations of the first RU and the second RU if the downlink signal is received from the first RU through the first antenna.

Abstract: A method and user equipment for transmitting a message of a random access procedure in a multi-beam system includes: transmitting and retransmitting a message 1 of the RA procedure through a first beam of a plurality of transmission beams of the UE based on power ramping; and retransmitting, if one or more Msg. 2 (RAR) is not successfully received corresponding to the message 1 transmission/retransmission, the message 1 through a second beam of the plurality of transmission beams after switching the first beam to the second beam at a second power level which is the same as or higher than a first power level of the first beam.

Abstract: A method and a terrestrial base station for receiving an uplink signal. The terrestrial base station is configured to: receive a preamble corresponding to an orthogonal pseudo-noise (PN) sequence of a plurality of the orthogonal PN sequences from an onboard base station in a train; recognize identification (ID) of the onboard base station from the preamble, and allocate a temporary network ID and an uplink grant (UL grant) to the onboard base station; and receive the uplink signal transmitted based on the temporary network ID and the UL grant.