Radio link monitoring in shared spectrum
A WTRU may be configured to perform radio link monitoring (RLM) based on RLM reference signals (RLM-RSs) transmitted in a cell operating in an unlicensed spectrum. The WTRU may evaluate a radio link failure (RLF) status for the cell using a first RLM criteria based on the RLM-RSs. A transmission instance of the RLM-RSs may be skipped, for example, due to a listen before talk (LBT) failure at a gNodeB (gNB). The WTRU may adapt or change the first RLM criteria and/or evaluate the RLF status of the cell operating in the unlicensed spectrum using a second RLM criteria based on determining that the transmission instance of the RLM-RSs was skipped. The first RLM criteria may correspond to a first RLM process that utilizes a first set of RLM parameters. The second RLM criteria may correspond to a second RLM process that utilizes a second set of RLM parameters.
1. A wireless transmit/receive unit (WTRU), comprising:
a processor configured to:
determine a maximum number of listen before talk (LBT) failures value;
perform a plurality of LBT procedures associated with a first bandwidth part (BWP) of a serving cell;
determine that a number of LBT failures corresponding to the maximum number of LBT failures value has been detected for the first BWP of the serving cell;
select a second BWP of the serving cell based on the determination that the number of LBT failures corresponding to the maximum number of LBT failures value has been detected for the first BWP of the serving cell, wherein the second BWP of the serving cell is selected based on a channel availability associated with the second BWP;
perform a LBT procedure associated with the second BWP of the serving cell;
determine that the LBT procedure associated with the second BWP of the serving cell is successful; and
perform a random access procedure associated with the second BWP of the serving cell, wherein the processor being configured to perform the random access procedure comprises the processor being configured to:
select a preamble associated with the second BWP; and
transmit the selected preamble to a base station, wherein an explicit indication is sent via the second BWP that indicates that the number of LBT failures corresponding to the maximum number of LBT failures value has been detected.
2. The WTRU of claim 1 , wherein the explicit indication that indicates that the number of LBT failures corresponding to the maximum number of LBT failures has been detected is sent to the base station as part of the random access procedure.
3. The WTRU of claim 1 , wherein the first BWP of the serving cell is active at a first time, a number of LBT failures associated with the first BWP of the serving cell is equal to or greater than a preconfigured value, and the second BWP of the serving cell is active at a second time, wherein the processor is further configured to determine that a number of LBT failures associated with the second BWP of the serving cell is less than the preconfigured value.
4. The WTRU of claim 3 , wherein the serving cell comprises a plurality of BWPs, and the first BWP is an initial BWP of the plurality of BWPs and is inactive at the second time.
5. The WTRU of claim 1 , wherein the processor is configured to determine that the number of LBT failures corresponding to the maximum number of LBT failures value has been detected for the first BWP of the serving cell based on a counter that counts a number of LBT failures associated with the first BWP of the serving cell.
6. The WTRU of claim 5 , wherein the processor is further configured to increment the counter based on a LBT failure of the number of LBT failures associated with the first BWP of the serving cell.
7. The WTRU of claim 1 , wherein the processor is further configured to transmit an uplink (UL) transmission over the second BWP of the serving cell.
8. The WTRU of claim 7 , wherein the processor being configured to select the second BWP of the serving cell based on the channel availability associated with the second BWP comprises the processor being configured to:
determine that there are a plurality of BWPs associated with the serving cell, wherein the plurality of BWPs comprises the second BWP;
determine that the second BWP has an earliest channel availability among the plurality of BWPs; and
select the second BWP based on the second BWP having the earliest channel availability.
9. A method, comprising:
determining a maximum number of listen before talk (LBT) failures value;
performing a plurality of LBT procedures associated with a first bandwidth part (BWP) of a serving cell;
determining that a number of LBT failures corresponding to the maximum number of LBT failures value has been detected for the first BWP of the serving cell;
selecting a second BWP of the serving cell based on determining that the number of LBT failures corresponding to the maximum number of LBT failures value has been detected for the first BWP of the serving cell, wherein the second BWP of the serving cell is selected based on a channel availability associated with the second BWP;
performing a LBT procedure associated with the second BWP of the serving cell;
determining that the LBT procedure associated with the second BWP of the serving cell is successful; and
performing a random access procedure associated with the second BWP of the serving cell, wherein performing the random access procedure comprises:
selecting a preamble associated with the second BWP; and
transmitting the selected preamble to a base station, wherein an explicit indication is sent via the second BWP that indicates that the number of LBT failures corresponding to the maximum number of LBT failures value has been detected.
10. The method of claim 9 , wherein the explicit indication that indicates that the number of LBT failures corresponding to the maximum number of LBT failures has been detected is sent to the base station as part of the random access procedure.
11. The method of claim 9 , wherein the first BWP of the serving cell is active at a first time, a number of LBT failures associated with the first BWP of the serving cell is equal to or greater than a preconfigured value, and the second BWP of the serving cell is active at a second time, the method further comprising determining that a number of LBT failures associated with the second BWP is less than the preconfigured value.
12. The method of claim 11 , wherein the serving cell comprises a plurality of BWPs, and the first BWP is an initial BWP of the plurality of BWPs and is inactive at the second time.
13. The method of claim 9 , wherein the determination that the number of LBT failures corresponding to the maximum number of LBT failures value has been detected for the first BWP of the serving cell is based on a counter that counts a number of LBT failures associated with the first BWP of the serving cell.
14. The method of claim 13 , further comprising incrementing the counter based on a LBT failure of the number of LBT failures associated with the first BWP of the serving cell.
15. The method of claim 9 , further comprising transmitting an uplink (UL) transmission over the second BWP of the serving cell.
16. The method of claim 15 , wherein selecting the second BWP of the serving cell based on the channel availability associated with the second BWP comprises:
determining that there are a plurality of BWPs associated with the serving cell, wherein the plurality of BWPs comprises the second BWP;
determining that the second BWP has an earliest channel availability among the plurality of BWPs; and
selecting the second BWP based on the second BWP having the earliest channel availability.