Method and apparatus for monitoring a wireless link in a wireless communication system

Abstract

The present invention relates to a wireless communication system, and more particularly to a method and apparatus for monitoring a wireless link. A method for monitoring a wireless link by a terminal in a wireless communication system according to one embodiment of the present invention comprises the steps of: receiving a precoded control channel; and estimating the quality of the wireless link for the received precoded control channel, wherein the quality of the wireless link can be estimated on the basis of an assumption by the terminal regarding the precoding applied to the precoded control channel.

The invention claimed is: 
     
       1. A method for performing radio link monitoring (RLM) by a user equipment (UE) in a wireless communication system, the method comprising:
 receiving a precoded control channel from a base station (BS); and   estimating a radio link quality of the received precoded control channel,   wherein the radio link quality is estimated on the basis of UE assumption associated with precoding applied to the precoded control channel,   wherein the UE assumption indicates that the precoding is carried out using a space-time code scheme,   wherein a 2n th  resource element of the precoded control channel includes a 2n th  modulation symbol transmitted from a first antenna of the BS and a (2n+1) th  modulation symbol transmitted from a second antenna of the BS,   wherein a (2n+1) th  resource element of the precoded control channel includes a (2n+1) th  modulation symbol transmitted from the first antenna and a negative conjugate of a 2n th  modulation symbol transmitted from the second antenna, and   wherein n is an integer equal to or greater than 0.   
     
     
       2. The method according to  claim 1 , wherein information regarding the precoding applied to the precoded control channel is transparent to the user equipment (UE). 
     
     
       3. The method according to  claim 1 , wherein the precoded control channel is an Enhanced-Physical Downlink Control Channel (E-PDCCH). 
     
     
       4. A user equipment (UE) for performing radio link monitoring (RLM) in a wireless communication system, comprising:
 a reception (Rx) module configured to receive a downlink signal from a base station (BS);   a transmission (Tx) module configured to transmit an uplink signal to the BS; and   a processor configured to control the UE including the reception (Rx) module and the transmission (Tx) module,   wherein the processor receives a precoded control channel through the reception (Rx) module, estimates a radio link quality of the received precoded control channel,   wherein the radio link quality is estimated on the basis of UE assumption associated with precoding applied to the precoded control channel,   wherein the UE assumption indicates that the precoding is carried out using a space-time code scheme,   wherein a 2n th  resource element of the precoded control channel includes a 2n th  modulation symbol transmitted from a first antenna of the BS and a (2n+1) th  modulation symbol transmitted from a second antenna of the BS,   wherein a (2n+1) th  resource element of the precoded control channel includes a (2n+1) th  modulation symbol transmitted from the first antenna and a negative conjugate of a 2n th  modulation symbol transmitted from the second antenna, and   wherein n is an integer equal to or greater than 0.   
     
     
       5. A method of performing a radio link monitoring by a user equipment (UE) configured with a plurality of cells in a wireless communication system, the method comprising:
 receiving, from a base station (BS), information regarding a set of resources of a first cell for the radio link monitoring;   performing the radio link monitoring for the first cell only excluding other cells among the plurality of cells, based on the set of resources of the first cell; and   determining whether a result of the radio link monitoring is ‘out-of-synchronization’ or ‘in-synchronization’ based on a first threshold value (Q out ) and a second threshold value (Q in ),   wherein the result of the radio link monitoring is determined to be ‘out-of-synchronization’ based on that all radio link qualities of all resources in the set of resources of the first cell other than the other cells is less than the first threshold value (Q out ),   wherein the result of the radio link monitoring is determined to be ‘in-synchronization’, based on that any radio link quality of any resource in the set of resources of the first cell other than the other cells is greater than the second threshold value (Q in ), and   wherein the information regarding the set of resources includes information for configuring that at least one signal including a first channel state information-reference signal (CSI-RS) is set as a reference signal (RS) for the radio link monitoring from among a plurality of CSI-RSs configured in the UE.   
     
     
       6. The method of claim 5, wherein the radio link monitoring performed based on the first CSI-RS is related to an error rate of a control channel which is determined based on a predetermined number of control channel symbols and a control channel-to-CSI-RS energy ratio. 
     
     
       7. A non-transitory computer-readable medium storing program codes for performing the method of claim 5. 
     
     
       8. A user equipment (UE) configured with a plurality of cells in a wireless communication system, the UE comprising:
 a transceiver configured to transmit and receive a radio signal with a base station (BS); and   a processor configured to control the transceiver,   wherein the processor is further configured to:
 receive, from a base station (BS), information regarding a set of resources of a first cell for the radio link monitoring; 
 perform the radio link monitoring for the first cell only excluding other cells among the plurality of cells, based on the set of resources of the first cell; and 
 determine whether a result of the radio link monitoring is ‘out-of-synchronization’ or ‘in-synchronization’ based on a first threshold value (Q out ) and a second threshold value (Q in ), 
 wherein the result of the radio link monitoring is determined to be ‘in-synchronization’, based on that any radio link quality of any resource in the set of resources of the first cell other than the other cells is greater than the second threshold value (Q in ), and 
 wherein the information regarding the set of resources includes information for configuring that at least one signal including a first channel state information-reference signal (CSI-RS) is set as a reference signal (RS) for the radio link monitoring from among a plurality of CSI-RSs configured in the UE. 
   
     
     
       9. The UE of claim 8, wherein the radio link monitoring performed based on the first CSI-RS is related to an error rate of a control channel which is determined based on a predetermined number of control channel symbols and a control channel-to-CSI-RS energy ratio.