Method and Apparatus for Radio Link Monitoring

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).

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).

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.