Method and device for random access for beam failure recovery
A method for random access for beam failure recovery. In the method, a random access configuration for the beam failure recovery is received. In the event of a beam failure, a random access procedure is performed according to the random access configuration.
1. A method in a user equipment in a network comprising:
receiving a message comprising a random access configuration for beam failure recovery from the network, wherein the random access configuration comprises at least a maximum number of preamble transmission attempts;
determining a beam failure event;
performing a random access procedure for beam failure recovery using the random access configuration, the random access procedure comprises:
selecting at least one candidate beam with a Reference Signal Received Power (RSRP) higher than a threshold; and
attempting random access via the selected at least one candidate beam with the RSRP higher than the threshold by sequencing through each selected at least one candidate beam from highest RSRP to lowest RSRP, including re-attempting the random access via one or more of the selected at least one candidate beam; and
stopping the random access procedure when:
the random access procedure is successful;
a radio link failure (RLF) timer expires; or
the maximum number of the preamble transmission attempts is reached prior to the RLF timer expiring.
2. The method according to claim 1 , wherein the random access configuration further comprises one or more of the following parameters:
a size of random access response window; and
a contention free random access resource.
3. The method according to claim 1 further comprising:
generating an indication that the random access procedure is for the beam failure recovery.
4. A user equipment comprising:
a processor; and
a memory containing instructions which, when executed by said processor, cause said user equipment to:
receive a message comprising a random access configuration for beam failure recovery from a network, wherein the random access configuration comprises at least a maximum number of preamble transmission attempts;
determine a beam failure event;
perform a random access procedure for beam failure recovery using the random access configuration, the random access procedure to:
select at least one candidate beam with a Reference Signal Received Power (RSRP) higher than a threshold; and
attempt random access via the selected at least one candidate beam with the RSRP higher than the threshold by sequencing through each selected at least one candidate beam from highest RSRP to lowest RSRP, including re-attempting the random access via one or more of the selected at least one candidate beam; and
stop the random access procedure when:
the random access procedure is successful;
a radio link failure (RLF) timer expires; or
the maximum number of the preamble transmission attempts is reached prior r expiring.
5. The user equipment according to claim 4 , wherein the random access configuration further comprises one or more of the following parameters:
a size of random access response window; and
a contention free random access resource.
6. The user equipment according to claim 4 , wherein the user equipment is further to generate an indication that the random access procedure is for the beam failure recovery.
7. A base station comprising:
a processor; and
a memory containing instructions which, when executed by said processor, cause said base station to:
set a random access configuration for beam failure recovery, wherein the random access configuration comprises at least a maximum number of preamble transmission attempts; and
transmit a message comprising the random access configuration for beam failure recovery to a user equipment (UE), in order for the UE to determine a beam failure event, and in order for the UE to perform a random access procedure for beam failure recovery using the random access configuration, the random access procedure to:
select at least one candidate beam with a Reference Signal Received Power (RSRP) higher than a threshold; and
attempt random access via the selected at least one candidate beam with the RSRP higher than the threshold by sequencing through each selected at least one candidate beam from highest RSRP to lowest RSRP, including re-attempting the random access via one or more of the selected at least one candidate beam;
wherein the UE stops the random access procedure when:
the random access procedure is successful;
a radio link failure (RLF) timer expires; or
the maximum number of the preamble transmission attempts is reached prior to the RLF timer expiring.
8. The base station according to claim 7 , wherein the random access configuration further comprises one or more of the following parameters:
a size of random access response window; and
a contention free random access resource.
9. The base station according to claim 7 , wherein the base station is further to receive an indication that the random access procedure is for the beam failure recovery.