Channel access methods and listen-before-talk solutions for new radio operation in unlicensed bands
Methods, systems, and devices for channel access and listen-before-talk approaches for new radio operation in unlicensed bands and/or licensed bands. A gNB and a wireless transmit/receive unit (WTRU) may operate in unlicensed spectrum. The gNB may perform listen-before-talk operation, and when successful, may send a downlink control channel with a slot format indication (SFI) to the WTRU. There may also be a handshaking procedure with an exchange of a request to transmit (RTT) and a request to receive (RTR). Prior to receiving the downlink channel, the WTRU may monitor search spaces at a first level, and once the downlink channel is received the WTRU may monitor search spaces at a second level. At the end of transmission, the WTRU may revert back to monitoring search spaces at the first level. In one example, the first level may be a mini-slot level and the second level may be a slot level.
1. A method implemented by a wireless transmit receive unit (WTRU), the method comprising:
monitoring for a transmission on a physical downlink control channel (PDCCH);
receiving the transmission, wherein the transmission includes configuration information, wherein the configuration information includes a channel occupancy time (COT);
monitoring for a first scheduling transmission on the PDCCH in a first set of search spaces at a first rate based on the configuration information; and
monitoring for a second scheduling transmission on the PDCCH in a second set of search spaces at a second rate on a condition that the COT has expired.
2. The method of claim 1 , wherein the WTRU switches from monitoring for the first scheduling transmission directly to monitoring for the second scheduling transmission.
3. The method of claim 1 , further comprising, prior to monitoring for the first scheduling transmission, monitoring in the second set of search spaces space at the second rate, and switching directly to monitoring for the first scheduling transmission based on the configuration information.
4. The method of claim 1 , wherein the transmission further includes a first slot format indicator (SFI) and a second SFI.
5. The method of claim 4 , wherein the monitoring for the first scheduling transmission is based on a first slot format indicated in the first SFI.
6. The method of claim 4 , wherein the monitoring for the second scheduling transmission is based on a second slot format indicated in the second SFI.
7. A wireless transmit receive unit (WTRU), comprising:
a processor;
a transceiver operatively coupled to the processor, the transceiver and processor configured to:
monitor for a transmission on a physical downlink control channel (PDCCH) receive the transmission, wherein the transmission includes configuration information, wherein the configuration information includes a channel occupancy time (COT);
monitor for a first scheduling transmission on the PDCCH in a first set of search spaces at a first rate based on the configuration information; and
monitor for a second scheduling transmission on the PDCCH in a second set of search spaces at a second rate on a condition that the COT has expired.
8. The WTRU of claim 7 , wherein the WTRU switches from monitoring for the first scheduling transmission directly to monitoring for the second scheduling transmission.
9. The WTRU of claim 7 , wherein prior to monitoring for the first scheduling transmission, the transceiver and processor are further configured to monitor in the second set of search spaces space at the second rate, and switch directly to monitoring for the first scheduling transmission based on the configuration information.
10. The WTRU of claim 7 , wherein the transmission further includes a first slot format indicator (SFI) and a second SFI.
11. The WTRU of claim 10 , wherein the monitoring for the first scheduling transmission is based on a first slot format indicated in the first SFI.
12. The WTRU of claim 10 , wherein the monitoring for the second scheduling transmission is based on a second slot format indicated in the second SFI.
13. A method implemented by a wireless transmit receive unit (WTRU), the method comprising:
monitoring for a transmission on a physical downlink control channel (PDCCH);
receiving the transmission, wherein the transmission includes configuration information, wherein the configuration information includes a channel occupancy time (COT);
monitoring for a first scheduling transmission in a first set of search spaces space at a first rate on the PDCCH;
switching directly to monitoring for a second scheduling transmission in a second set of search spaces at a second rate on the PDCCH based on the configuration information; and
switching directly to monitoring for the first scheduling transmission in the first set of search spaces at the first rate on the PDCCH on a condition that the COT has expired.