Channel sensing for physical random access channel (PRACH) signals in new radio (NR) systems operating in the unlicensed spectrum
A user equipment (UE), or other network component can operate to configure channel occupancy time (COT) sharing in random access procedures involving the unlicensed spectrum. At least some of the messages for the procedures can share a COT by configuring one or more gaps or listen-before-talk (LBT) procedures based on the gap or whether the COT sharing is UE or gNB initiated. Some configurations can depend on a location in the random access procedure that COT sharing is acquired.
1. An apparatus employed in a user equipment (UE), comprising processing circuitry configured to:
generate and cause transmission of a first message comprising a preamble of a random access channel (RACH);
receive, from a base station, a second message indicating a reception of the preamble and comprising a time-adjustment command and a scheduling grant via a physical downlink channel;
generate and cause transmission of a third message based on a resource indicated by the scheduling grant of the second message;
receive, from the base station, a fourth message comprising contention resolution information; and
generate a hybrid automatic repeat request (HARQ) feedback based on the fourth message,
wherein the third message includes a listen-before-talk (LBT) indication that indicates which LBT type the base station is to perform, and wherein the LBT indication comprises one bit of an uplink control information (UCI).
2. The apparatus of claim 1 , wherein the LBT indication comprises two bits of an uplink control information (UCI).
3. The apparatus of claim 1 , wherein the second message comprises a random access response (RAR) message.
4. The apparatus of claim 1 , wherein a channel access priority class (CAPC) is indicated by the third message. .
5. The apparatus of claim 1 , wherein the processing circuitry is further configured to configure the third message to share a channel occupancy time (COT) with the second message based on a gap therebetween that is sixteen microseconds or twenty-five microseconds.
6. A method for a base station, comprising:
receiving a first message from a user equipment (UE), the first message comprising a preamble of a random access channel (RACH) configured to perform a random access procedure;
generating and transmitting a second message that indicates a reception of the preamble and comprising a time-adjustment command and a scheduling grant via a physical downlink channel for configuring a third message;
receiving the third message from the UE based on a resource indicated by the scheduling grant of the second message;
generating and transmitting a fourth message to transfer the UE to a connected state; and
receiving a HARQ feedback from the UE based on the fourth message,
wherein the third message includes a listen-before-talk (LBT) indication that indicates which LBT type the base station is to perform,
wherein the third message comprises a UCI that includes two bits that comprise the LBT indication.
7. The method of claim 6 , wherein the second message comprises random access response (RAR).
8. A method for a user equipment (UE), comprising:
generating a first message comprising a preamble of a random access channel (RACH);
receiving a second message indicating a reception of the preamble and comprising a scheduling grant via a physical downlink channel;
generating a third message based on a resource indicated by the scheduling grant of the second message;
receiving a fourth message comprising contention resolution information; and
generating a hybrid automatic repeat request (HARQ) feedback based on the fourth message;
wherein the third message includes a listen-before-talk (LBT) indication that indicates which LBT type a base station is to perform, and
wherein at least two of: the first message, the second message, the third message, the fourth message, or the HARQ feedback share a channel occupancy time (COT) in a random access procedure, wherein the HARQ feedback is transmitted within 16 microseconds of the fourth message.
9. The method of claim 8 , wherein the LBT indication comprises two bits of an uplink control information (UCI).
10. The method of claim 8 , wherein the LBT indication comprises one bit of an uplink control information (UCI).
11. The method of claim 8 , wherein the second message comprises a random access response (RAR) message.
12. The method of claim 8 , wherein a channel access priority class (CAPC) is indicated by the third message.
13. The apparatus of claim 1 , wherein the one bit in the UCI that indicates LBT is a channel occupancy time (COT) sharing bit.
14. The method of claim 6 , wherein a first bit of the two bits that comprise the LBT indication is a channel occupancy time (COT) sharing bit.
15. The method of claim 8 , wherein the third message includes a COT sharing bit.