Method and apparatus for random access in mobile communication system
地域：
Daejeon
摘要
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.
說明書
This application claims priority to and the benefit of Korean Patent Application Nos. 10-2017-0037828 and 10-2018-0034090 filed in the Korean Intellectual Property Office on Mar. 24, 2017 and Mar. 23, 2018, the entire contents of which are incorporated herein by reference.
The present invention relates to a method and an apparatus for random access in a mobile communication system.
Beamforming technology is one of next generation communication technologies for processing wireless data traffic that are expanding. The beamforming-based mobile communication system uses a high frequency band to transmit signals, and beamforming can be performed in a base station and a terminal such that a beam forming gain is increased in a specific direction using a large number of antennas. In a beamforming-based mobile communication system, a beam sweeping operation is performed to transmit or receive a signal while changing a plurality of beams.
In a beamforming-based mobile communication system, a base station and a terminal operate a plurality of beams, and the base station transmits a reference signal for each beam so that the terminal can measure a channel state of each beam. For example, if the terminal informs the base station of the optimal transmission beam index of the base station, the base station transmits data to the terminal using the optimal transmission beam.
權(quán)利要求
What is claimed is:1. A method for random access in a multi-beam-based mobile communication system, comprising:receiving, by a terminal, a plurality of synchronization signal blocks from a base station; obtaining, by the terminal, a beam index and a beam group index included in one synchronization signal block among the received plurality of synchronization signal blocks; identifying, by the terminal, a random access resource associated with the beam group index which indicates a first beam group to which a first beam used for transmitting the one synchronization signal block belongs; identifying, by the terminal, a plurality of preamble resources included in the random access resource based on the beam index indicating the first beam; and transmitting, by the terminal, a preamble message using the plurality of preamble resources to the base station, wherein each of the plurality of synchronization signal blocks is specified for one beam and the plurality of preamble resources are used for transmitting the preamble message by the terminal. 2. The method of claim 1 , wherein the terminal recognizes the first beam corresponding to the obtained beam index as an optimal downlink transmission beam, andthe plurality of preamble resources includes a central preamble resource corresponding to the beam index and preamble resources which are located prior to and after the central preamble resource corresponding to the beam index. 3. The method of claim 1 , wherein a beam specified for a preamble resource located in a middle among the plurality of preamble resources on which the preamble message is transmitted is recognized by the base station as an optimal downlink transmission beam for the terminal. 4. The method of claim 1 , wherein, when beam grouping is performed, a burst including the plurality of synchronization signal blocks corresponds to one random access resource, and the plurality of synchronization signal blocks of the burst correspond to different preamble resources in the random access resource. 5. The method of claim 1 , wherein the obtaining of the beam index and the beam group index comprises:selecting, by the terminal, the one synchronization signal block corresponding to a direction of the terminal from among the plurality of synchronization signal blocks; and decoding, by the terminal, the selected one synchronization signal block to obtain the beam index and the beam group index. 6. The method of claim 1 , wherein the random access resource includes the plurality of preamble resources and a guard time (GT) resource, andwherein the transmitting of the preamble message comprises, when an optimal beam recognized according to the beam index is an initial or last beam and a length of the preamble message is predetermined, selecting preamble resources from a first preamble resource or a last preamble resource of the random access resource by the length of the preamble message and transmitting the preamble message by using the selected preamble resources. 7. The method of claim 1 , further comprising: after the transmitting of a preamble message,receiving, by the terminal, at least one random access response (RAR) transmitted on RAR resources selected through a RAR selection procedure from the base station; selecting, by the terminal, a RAR from among a plurality of RARs when receiving the plurality of RARs; and recognizing, by the terminal, that a beam corresponding to the selected RAR is an optimal uplink reception beam. 8. The method of claim 7 , wherein a RAR resource is specified to one beam and corresponds to one preamble resource of the random access resource, andwherein the selecting of a RAR from among a plurality of RARs comprises, when a plurality of terminals are respectively located in different cover ridges and each terminal transmits a preamble message including a different preamble sequence, selecting one RAR from among the plurality of RARs based on a preamble sequence used in the preamble message transmission. 9. The method of claim 7 , wherein a RAR resource is specified to one beam and corresponds to one preamble resource of the random access resource, andwherein the selecting of a RAR from among a plurality of RARs comprises, when a plurality of terminals are respectively located in different cover ridges and each terminal transmits a preamble message including a same preamble sequence, selecting one RAR having maximum reception power. 10. The method of claim 7 , wherein the RAR selection procedure at the base station is performed based on a preamble message having maximum reception power among a plurality of preamble messages, and a beam corresponding to a preamble resource on which the preamble message having maximum reception power is transmitted is selected as an optimal beam, and wherein the RAR from the base station is transmitted on RAR resources corresponding to the selected optimal beam. 11. A method for random access in a multi-beam-based mobile communication system, comprising:transmitting, by a base station, a plurality of synchronization signal blocks; monitoring, by the base station, a plurality of preamble resources associated with each of the plurality of synchronization signal blocks; receiving, by the base station, a preamble message in the plurality of preamble resources associated with one synchronization signal block among the plurality of synchronization signal blocks from a terminal; and recognizing, by the base station, a first beam specified to the one synchronization signal block corresponding to the plurality of preamble resources, the preamble message being received on the plurality of preamble resources, as an optimal downlink transmission beam for the terminal, wherein a random access resource includes the plurality of preamble resources, the one synchronization signal block is specified for one beam, the plurality of preamble resources are used for transmitting the preamble message by the terminal, each of the plurality of synchronization signal blocks includes a beam index and a beam group index, the beam index included in the one synchronization signal block indicates the first beam, the beam group index included in the one synchronization signal block indicates a first beam group to which the first beam belongs, the first beam group is associated with the random access resource, and the first beam is associated with the plurality of preamble resources included in the random access resource. 12. The method of claim 11 , wherein the recognizing comprises recognizing the first beam specified for the one synchronization signal block corresponding to a preamble resource located in a middle among the plurality of preamble resources on which the preamble message is received as the optimal downlink transmission beam for the terminal. 13. The method of claim 11 , wherein the plurality of preamble resources includes a preamble resource corresponding to the beam index included in the one synchronization signal block and preamble resources which are located prior to and after the preamble resource corresponding to the beam index. 14. The method of claim 11 , further comprising:after the recognizing, selecting, by the base station, an optimal uplink reception beam for the terminal by beam sweeping; and transmitting, by the base station, a random access response (RAR) on RAR resources corresponding to the selected beam, wherein a RAR resource is specified to one beam and corresponds to one preamble resource of the random access resource. 15. The method of claim 14 , wherein the selecting of the optimal uplink reception beam comprises selecting the optimal uplink reception beam based on maximum reception power. 16. A method for random access in a multi-beam-based mobile communication system, comprising:monitoring, by a terminal, resources with a resource window of a fixed length after transmitting a preamble message; receiving, by the terminal, a plurality of random access responses (RARs) transmitted on RAR resources selected through a RAR selection procedure from the base station according to the monitoring; selecting, by the terminal, an RAR from among the plurality of RARs; and recognizing, by the terminal, that a beam corresponding to the selected RAR is an optimal reception beam of the terminal, wherein a random access resource includes a plurality of preamble resources, and each of the RAR resources is specified to different beams and corresponds to different preamble resources of the random access resource, and wherein in the selecting the RAR by the terminal, when each of a plurality of terminals including the terminal transmits the preamble message with a different preamble sequence, the terminal selects the RAR based on a preamble sequence used for transmitting the preamble message, and when each of the plurality of terminals transmits the preamble message with a same preamble sequence, the terminal selects an RAR among the plurality of RARs having a maximum reception power. 17. The method of claim 16 , whereinthe plurality of terminals are respectively located in different cover ridges. 18. The method of claim 16 , further comprising:before the monitoring, receiving, by the terminal, a synchronization signal block and obtaining beam index information from the received synchronization signal block; and transmitting, by the terminal, the preamble message, the preamble message occupying the plurality of preamble resources, the plurality of preamble resources including a preamble resource corresponding to the beam index information to the base station, wherein the synchronization signal block is specified for one beam or one beam group and corresponds to one preamble resource of the random access resource. 19. The method of claim 18 , wherein the transmitting of the preamble message comprises transmitting the preamble message by using the plurality of preamble resources including a preamble resource corresponding to the beam index information and preamble resources which are located on a left and right of the preamble resource corresponding to the beam index information.
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