Rach quasi-colocation association
In an aspect of the disclosure, a method, a computer-readable medium, and an apparatus are provided. The apparatus may be a UE. The UE determines that a random access event has occurred. The UE detects one or more down-link reference signals that are UE-specifically configured or predefined. The UE further selects a first message that is associated with a first down-link reference signal of the one or more down-link reference signals, the first down-link reference signal being quasi-colocated with a first DMRS of a serving control channel of the UE. The UE sends the first message to a base station to request a random access to the base station.
1. A method of wireless communication of a user equipment (UE), comprising:
receiving a first Demodulation Reference Signal (DMRS) on a serving control channel of the UE;
determining that a random access event has occurred;
receiving a plurality of down-link reference signals each being a Synchronization Signal Block (SSB) or a channel state information reference signal (CSI-RS);
selecting a first down-link reference signal from the plurality of down-link reference signals, the first down-link reference signal being quasi-colocated with the first DMRS and UE-specifically configured or predefined;
selecting a first message from a group of messages that each are associated with the first down-link reference signal; and
sending the first message to a base station to request a random access to the base station.
2. The method of claim 1 , wherein the first message includes a preamble sequence, wherein the first message is selected from a group of messages that are associated with the first down-link reference signal.
3. The method of claim 1 , wherein the first down-link reference signal is a synchronization signal block.
4. The method of claim 1 , wherein the first down-link reference signal is directly quasi-colocated with the first DMRS.
5. The method of claim 1 , wherein the first down-link reference signal is quasi-colocated with the first DMRS through one or more intermediate signals.
6. The method of claim 1 , wherein, when the UE is in a connected state, the random access event includes at least one of:
reception of a request from the base station to initiate a random access to the base station;
a handover of the UE from a second base station to the base station;
an up-link data arrival without up-link synchronization;
a down-link data arrival without up-link synchronization; and
a beam failure recovery request.
7. The method of claim 6 , further comprising:
receiving a second message from the base station in response to the first message by assuming that a DMRS included in the request and a DMRS included in the second message are quasi-colocated.
8. The method of claim 7 , wherein the random access event is the reception of the request, wherein the request is a physical downlink control channel (PDCCH) order, wherein the second message includes a PDCCH command and a random access response.
9. The method of claim 7 , wherein the random access event is the beam failure recovery request, wherein the second message is scrambled by a cell radio network temporary identifier (C-RNTI) of the UE.
10. An apparatus for wireless communication, the apparatus being a user equipment (UE), comprising:
a memory; and
at least one processor coupled to the memory and configured to:
receive a first Demodulation Reference Signal (DMRS) on a serving control channel of the UE;
determine that a random access event has occurred;
receive a plurality of down-link reference signals each being a Synchronization Signal Block (SSB) or a channel state information reference signal (CSI-RS);
select a first down-link reference signal from the plurality of down-link reference signals, the first down-link reference signal being quasi-colocated with the first DMRS and UE-specifically configured or predefined;
select a first message from a group of messages that each are associated with the first down-link reference signal; and
send the first message to a base station to request a random access to the base station.
11. The apparatus of claim 10 , wherein the first message includes a preamble sequence, wherein the first message is selected from a group of messages that are associated with the first down-link reference signal.
12. The apparatus of claim 10 , wherein the first down-link reference signal is a synchronization signal block.
13. The apparatus of claim 10 , wherein the first down-link reference signal is directly quasi-colocated with the first DMRS.
14. The apparatus of claim 10 , wherein the first down-link reference signal is quasi-colocated with the first DMRS through one or more intermediate signals.
15. The apparatus of claim 10 , wherein, when the UE is in a connected state, the random access event includes at least one of:
reception of a request from the base station to initiate a random access to the base station;
a handover of the UE from a second base station to the base station;
an up-link data arrival without up-link synchronization;
a down-link data arrival without up-link synchronization; and
a beam failure recovery request.
16. The apparatus of claim 15 , wherein the at least one processor is further configured to:
receive a second message from the base station in response to the first message by assuming that a DMRS included in the request and a DMRS included in the second message are quasi-colocated.
17. The apparatus of claim 16 , wherein the random access event is the reception of the request, wherein the request is a physical downlink control channel (PDCCH) order, wherein the second message includes a PDCCH command and a random access response.
18. The apparatus of claim 16 , wherein the random access event is the beam failure recovery request, wherein the second message is scrambled by a cell radio network temporary identifier (C-RNTI) of the UE.
19. A non-transitory computer-readable medium storing computer executable code for wireless communication of wireless equipment, comprising code to:
receive a first Demodulation Reference Signal (DMRS) on a serving control channel of the UE;
determine that a random access event has occurred;
receive a plurality of down-link reference signals each being a Synchronization Signal Block (SSB) or a channel state information reference signal (CSI-RS);
select a first down-link reference signal from the plurality of down-link reference signals, the first down-link reference signal being quasi-colocated with the first DMRS and UE-specifically configured or predefined;
select a first message from a group of messages that each are associated with the first down-link reference signal; and
send the first message to a base station to request a random access to the base station.
20. The non-transitory computer-readable medium of claim 19 , wherein the first message includes a preamble sequence, wherein the first message is selected from a group of messages that are associated with the first down-link reference signal.