Method whereby user equipment operates in wireless communication system, and device for supporting same
Disclosed are a method whereby user equipment operates in a wireless communication system, and a device for supporting same. Disclosed more particularly are: a method whereby, in case a base station which operates multiple analogue beams is connected to user equipment, the user equipment determines a cell-level radio link failure (RLF) and a beam-level RLF through signal transmission and reception to and from the base station and carries out an operation based on the determination; and a device for supporting said method.
1. A method of operating by a user equipment (UE) connected to a base station (BS) operating a plurality of analog beams in a wireless communication system, the method comprising:
receiving from the BS, a cell-specific signal and a beam-specific signal corresponding to a serving beam of the BS;
determining cell-level radio link failure (RLF) and beam-level RLF, based on a result of receiving the cell-specific signal and the beam-specific signal; and
performing a corresponding operation according to a result of determining the cell-level RLF and the beam-level RLF.
2. The method of claim 1 , further comprising,
performing a radio resource control (RRC) connection re-establishment procedure upon determining that the cell-level RLF has occurred.
3. The method of claim 2 , further comprising:
when the RRC connection re-establishment procedure is successful, maintaining RRC connection with an evolved Node B (eNB); and
when the RRC connection re-establishment procedure fails, transitioning to an RRC-idle mode and performing a cell selection or cell reselection procedure.
4. The method of claim 1 , further comprising
performing a serving beam re-establishment procedure upon determining that the cell-level RLF has not occurred and the beam-level RLF has occurred.
5. The method of claim 4 , further comprising:
when the serving beam re-establishment procedure is successful, maintaining RRC connection with the BS using the serving beam; and
when the serving beam re-establishment procedure fails, initializing the serving beam and performing a beam recovery procedure for the BS.
6. The method of claim 5 , wherein the beam recovery procedure for the BS comprises:
transmitting information about a best beam preferred with respect to the BS or information about a channel of each beam to the BS;
receiving configuration information regarding a new serving beam from the BS based on the information transmitted to the BS; and
updating the serving beam for the UE using the configuration information regarding the new serving beam.
7. The method of claim 1 , further comprising:
upon determining that the cell-level RLF has not occurred and the beam-level RLF has not occurred, maintaining the serving beam for the BS until a serving beam release indication is received and maintaining radio resource control (RRC) connection with the BS until an RRC connection release indication is received.
8. The method of claim 1 , wherein the cell-specific signal includes at least one of:
a synchronization signal,
a demodulation reference signal (DM-RS) for a physical broadcast channel (PBCH), and
a signal which corresponds to the BS and is transmitted by applying a beam sweeping operation to the plurality of analog beams.
9. The method of claim 1 , wherein the beam-specific signal includes one or more of a reference signal for measuring channel state information corresponding to the serving beam and a signal having a quasi co-location (QCL) relationship with the serving beam.
10. The method of claim 1 , wherein the cell-level RLF is determined based on received strength of the cell-specific signal.
11. The method of claim 10 , further comprising:
calculating an average value of higher N (where N is a natural number) measurement values for the cell-specific signal in each time interval; and
determining the cell-level RLF based on a value obtained by applying time-axis filtering to the average value in each time interval.
12. The method of claim 1 , wherein the beam-level RLF is determined based on received strength of the beam-specific signal.
13. A user equipment (UE) connected to a base station (BS) which operates a plurality of analog beams in a wireless communication system, the UE comprising:
a transmitter;
a receiver; and
a processor connected to the transmitter and the receiver,
wherein the processor is configured to:
receive a cell-specific signal and a beam-specific signal corresponding to a serving beam of the BS, from the BS;
determine cell-level radio link failure (RLF) and beam-level RLF, based on a result of receiving the cell-specific signal and the beam-specific signal; and
perform a corresponding operation according to a result of determining the cell-level RLF and the beam-level RLF.