Method and Apparatus for Radio Link Monitoring

Abstract

Provided herein are method and apparatus for perform radio link monitoring (RLM) based on a Reference signal (RS). An embodiment provides a user Equipment (UE) comprising circuitry configured to: decode a Reference Signal (RS) received from an access node; and determine beam quality for one or more beam pair links (BPLs) of the RS between the UE and the access node based on the decoded RS, wherein each of the BPLs comprises a transmit (Tx) beam of the access node and a receive (Rx) beam of the UE. Also provided is a procedure of RLM. At least some embodiments allow for beam recovery request for UE beam refinement, and allow for determining whether radio link failure (RLF) occurs.

1 . (canceled) 
     
     
         2 . A method performed by a user equipment (UE) in a communications network, the method comprising:
 decoding a first Reference Signal (RS) received from an access node, the first RS related to radio link monitoring (RLM);   obtaining, based at least on the first RS, a first signal quality of at least one beam pair link (BPL) forming a communication channel between the UE and the access node, the at least one BPL including a transmit (Tx) beam of the access node and a receive (Rx) beam of the UE;   determining that the first signal quality for the at least one BPL is above a first threshold value;   in response to determining that the first signal quality for at least one communication channel is above the first threshold value, identifying an occurrence of an in-sync condition;   receiving a second RS from the access node, the second RS related to RLM;   obtaining, based at least on the second RS, a second signal quality of the at least one BPL;   determining that the second signal quality for the at least one BPL is below a second threshold value;   in response to determining that the second signal quality for the at least one BPL is below the second threshold value, identifying an occurrence of an out-of-sync condition;   determining that a number of consecutive out-of-syncs equals a threshold number; and   in response to determining that the number of consecutive out-of-syncs equals the threshold number, determining occurrence of radio link failure (RLF).   
     
     
         3 . The method of  claim 2 , wherein the RS includes one of a Synchronization Signal (SS) or a Channel State Information Reference Signal (CSI-RS). 
     
     
         4 . The method of  claim 2 , wherein determining the first signal quality or the second signal quality for the at least one BPL comprises measuring one of a Reference Signal Receiving Power (RSRP) or a Reference Signal Receiving Quality (RSRQ) of the first RS or the second RS, respectively. 
     
     
         5 . The method of  claim 2 , wherein identifying the occurrence of the out-of-sync condition comprises determining that the second signal quality is below the second threshold value for a predetermined time period. 
     
     
         6 . The method of  claim 2 , further comprising:
 in response to determining that the second signal quality for the at least one BPL is below the second threshold value, transmitting a beam recovery request to the access node.   
     
     
         7 . The method of  claim 6 , further comprising:
 receiving a Channel State Information Reference Signal (CSI-RS) from the access node in response to transmitting the beam recovery request to the access node; and   determining signal quality for one or more Rx beams of the UE based at least on the CSI-RS.   
     
     
         8 . The method of  claim 7 , further comprising:
 determining that out-of-sync occurs if the beam quality for the Rx beams is below the second threshold.   
     
     
         9 . The method of  claim 6 , further comprising:
 determining that a Channel State Information Reference Signal (CSI-RS) is not received from the access node within a specified time period after transmitting the beam recovery request; and   in response to the determination, transmitting a second beam recovery request to the access node.   
     
     
         10 . A processor for a user equipment (UE) in a communications network, the processor configured to perform operations comprising:
 decoding a first Reference Signal (RS) received from an access node, the first RS related to radio link monitoring (RLM);   obtaining, based at least on the first RS, a first signal quality of at least one beam pair link (BPL) forming a communication channel between the UE and the access node, the at least one BPL including a transmit (Tx) beam of the access node and a receive (Rx) beam of the UE;   determining that the first signal quality for the at least one BPL is above a first threshold value;   in response to determining that the first signal quality for at least one communication channel is above the first threshold value, identifying an occurrence of an in-sync condition;   receiving a second RS from the access node, the second RS related to RLM;   obtaining, based at least on the second RS, a second signal quality of the at least one BPL;   determining that the second signal quality for the at least one BPL is below a second threshold value;   in response to determining that the second signal quality for the at least one BPL is below the second threshold value, identifying an occurrence of an out-of-sync condition;   determining that a number of consecutive out-of-syncs equals a threshold number; and   in response to determining that the number of consecutive out-of-syncs equals the threshold number, determining occurrence of radio link failure (RLF).   
     
     
         11 . The processor of  claim 10 , wherein the RS includes one of a Synchronization Signal (SS) or a Channel State Information Reference Signal (CSI-RS). 
     
     
         12 . The processor of  claim 10 , wherein determining the first signal quality or the second signal quality for the at least one BPL comprises measuring one of a Reference Signal Receiving Power (RSRP) or a Reference Signal Receiving Quality (RSRQ) of the first RS or the second RS, respectively. 
     
     
         13 . The processor of  claim 10 , wherein identifying the occurrence of the out-of-sync condition comprises determining that the second signal quality is below the second threshold value for a predetermined time period. 
     
     
         14 . The processor of  claim 10 , wherein the operations further comprise:
 in response to determining that the second signal quality for the at least one BPL is below the second threshold value, transmitting a beam recovery request to the access node.   
     
     
         15 . The processor of  claim 14 , wherein the operations further comprise:
 receiving a Channel State Information Reference Signal (CSI-RS) from the access node in response to transmitting the beam recovery request to the access node; and   determining signal quality for one or more Rx beams of the UE based at least on the CSI-RS.   
     
     
         16 . The processor of  claim 15 , wherein the operations further comprise:
 determining that out-of-sync occurs if the beam quality for the Rx beams is below the second threshold.   
     
     
         17 . The processor of  claim 14 , wherein the operations further comprise:
 determining that a Channel State Information Reference Signal (CSI-RS) is not received from the access node within a specified time period after transmitting the beam recovery request; and   in response to the determination, transmitting a second beam recovery request to the access node.   
     
     
         18 . A method performed by an access node in a communications network, the method comprising:
 transmitting a Reference Signal (RS) to a user equipment (UE) in the communications network, the RS related to measuring signal quality of one or more communication channels between the UE and the access node for radio link monitoring (RLM), wherein a communication channel of the one or more communication channels is formed using a beam pair link (BPL) that includes a transmit (Tx) beam of the access node and a receive (Rx) beam of the UE;   receiving, from the UE, a beam recovery request that is generated based at least on a signal quality of at least one communication channel of the one of one or more communication channels, wherein the beam recovery request indicates a specified number of communication channels of the one of one or more communication channels for which respective signal qualities are below a threshold value; and   in response to receiving the beam recovery request, transmitting, to the UE, a Channel State Information Reference Signal (CSI-RS) corresponding to the specified number of communication channels.   
     
     
         19 . The method of  claim 18 , wherein the RS includes one of a Synchronization Signal (SS) or a CSI-RS. 
     
     
         20 . The method of  claim 18 , wherein the signal quality of the at least one communication channel includes one of a Reference Signal Receiving Power (RSRP) or a Reference Signal Receiving Quality (RSRQ). 
     
     
         21 . The method of  claim 18 , wherein transmitting the CSI-RS corresponding to the specified number of communication channels comprises encoding the CSI-RS with a specified number of Tx beams of the access node corresponding to the specified number of communication channels.