Resource Selection Using a Listen Before Talk Procedure
Wireless communications between a base station and one or more wireless devices are described. Multiple downlink reference signals may correspond to multiple random access resources for a random access procedure. A base station may provide a set of downlink reference signals before a set of physical random access channels (PRACHs) are available for use. A wireless device performing a random access procedure may select two or more random access resources (e.g., PRACH occasions) based on the downlink reference signals. Using a listen before talk (LBT) procedure, the wireless device may select a first available random access resource from the two or more random access resources that are determined to be clear.
1 . A method comprising:
receiving, by a wireless device, a plurality of downlink reference signals of a cell; and
based on a failure of a first listen-before-talk (LBT) procedure and a success of a second LBT procedure, transmitting, via a resource, a preamble for a random access procedure, wherein the resource is associated with a downlink reference signal of the plurality of downlink reference signals of the cell.
2 . The method of claim 1 , wherein the first LBT procedure is on a second resource associated with a second downlink reference signal of the plurality of downlink reference signals of the cell.
3 . The method of claim 1 , wherein each of the plurality of downlink reference signals of the cell comprises at least one of:
a synchronization signal and physical broadcast channel block (SSB); or
a channel state information reference signal (CSI RS).
4 . The method of claim 1 , further comprising:
receiving a radio resource control message indicating that the cell comprises a downlink carrier, a normal uplink carrier, and a supplementary uplink carrier; and
selecting, based on a received signal strength of one of the plurality of downlink reference signals, at least one of the normal uplink carrier or the supplementary uplink carrier.
5 . The method of claim 1 , further comprising:
determining, based on the failure of the first LBT procedure, the resource for random access.
6 . The method of claim 1 , wherein the resource comprises a physical random access channel resource.
7 . The method of claim 1 , further comprising:
determining a second resource for random access, wherein the second resource is associated with a second downlink reference signal of the plurality of downlink reference signals of the cell; and
determining, based on the failure of the first LBT procedure, that the second resource is occupied.
8 . The method of claim 1 , further comprising:
performing, based on the failure of the first LBT procedure, a resource selection procedure for random access, wherein the resource selection procedure selects the resource.
9 . A wireless device comprising:
one or more processors; and
memory storing instructions that, when executed by the one or more processors, cause the wireless device to:
receive a plurality of downlink reference signals of a cell; and
based on a failure of a first listen-before-talk (LBT) procedure and a success of a second LBT procedure, transmit, via a resource, a preamble for a random access procedure, wherein the resource is associated with a downlink reference signal of the plurality of downlink reference signals of the cell.
10 . The wireless device of claim 9 , wherein the first LBT procedure is on a second resource associated with a second downlink reference signal of the plurality of downlink reference signals of the cell.
11 . The wireless device of claim 9 , wherein each of the plurality of downlink reference signals of the cell comprises at least one of:
a synchronization signal and physical broadcast channel block (SSB); or
a channel state information reference signal (CSI RS).
12 . The wireless device of claim 9 , wherein the instructions, when executed by the one or more processors, further cause the wireless device to:
receive a radio resource control message indicating that the cell comprises a downlink carrier, a normal uplink carrier, and a supplementary uplink carrier; and
select, based on a received signal strength of one of the plurality of downlink reference signals, at least one of the normal uplink carrier or the supplementary uplink carrier.
13 . The wireless device of claim 9 , wherein the instructions, when executed by the one or more processors, further cause the wireless device to:
determine, based on the failure of the first LBT procedure, the resource for random access.
14 . The wireless device of claim 9 , wherein the resource comprises a physical random access channel resource.
15 . The wireless device of claim 9 , wherein the instructions, when executed by the one or more processors, further cause the wireless device to:
determine a second resource for random access, wherein the second resource is associated with a second downlink reference signal of the plurality of downlink reference signals of the cell; and
determine, based on the failure of the first LBT procedure, that the second resource is occupied.
16 . The wireless device of claim 9 , wherein the instructions, when executed by the one or more processors, further cause the wireless device to:
perform, based on the failure of the first LBT procedure, a resource selection procedure for random access, wherein the resource selection procedure selects the resource.
17 . One or more non-transitory computer-readable media storing instructions that, when executed, cause a wireless device to:
receive a plurality of downlink reference signals of a cell; and
based on a failure of a first listen-before-talk (LBT) procedure and a success of a second LBT procedure, transmit, via a resource, a preamble for a random access procedure, wherein the resource is associated with a downlink reference signal of the plurality of downlink reference signals of the cell.
18 . The one or more non-transitory computer-readable media of claim 17 , wherein the first LBT procedure is on a second resource associated with a second downlink reference signal of the plurality of downlink reference signals of the cell.
19 . The one or more non-transitory computer-readable media of claim 17 , wherein each of the plurality of downlink reference signals of the cell comprises at least one of:
a synchronization signal and physical broadcast channel block (SSB); or
a channel state information reference signal (CSI RS).
20 . The one or more non-transitory computer-readable media of claim 17 , wherein the instructions, when executed, further cause the wireless device to:
receive a radio resource control message indicating that the cell comprises a downlink carrier, a normal uplink carrier, and a supplementary uplink carrier; and
select, based on a received signal strength of one of the plurality of downlink reference signals, at least one of the normal uplink carrier or the supplementary uplink carrier.
21 . The one or more non-transitory computer-readable media of claim 17 , wherein the instructions, when executed, further cause the wireless device to:
determine, based on the failure of the first LBT procedure, the resource for random access.
22 . The one or more non-transitory computer-readable media of claim 17 , wherein the resource comprises a physical random access channel resource.
23 . The one or more non-transitory computer-readable media of claim 17 , wherein the instructions, when executed, further cause the wireless device to:
determine a second resource for random access, wherein the second resource is associated with a second downlink reference signal of the plurality of downlink reference signals of the cell; and
determine, based on the failure of the first LBT procedure, that the second resource is occupied.
24 . The one or more non-transitory computer-readable media of claim 17 , wherein the instructions, when executed, further cause the wireless device to:
perform, based on the failure of the first LBT procedure, a resource selection procedure for random access, wherein the resource selection procedure selects the resource.
25 . A system comprising:
a base station configured to send a plurality of downlink reference signals of a cell; and
a wireless device comprising:
one or more processors; and
memory storing instructions that, when executed by the one or more processors, cause the wireless device to:
receive the plurality of downlink reference signals of the cell; and
based on a failure of a first listen-before-talk (LBT) procedure and a success of a second LBT procedure, transmit, via a resource, a preamble for a random access procedure, wherein the resource is associated with a downlink reference signal of the plurality of downlink reference signals of the cell.
26 . The system of claim 25 , wherein the first LBT procedure is on a second resource associated with a second downlink reference signal of the plurality of downlink reference signals of the cell.
27 . The system of claim 25 , wherein each of the plurality of downlink reference signals of the cell comprises at least one of:
a synchronization signal and physical broadcast channel block (SSB); or
a channel state information reference signal (CSI RS).
28 . The system of claim 25 , wherein the instructions, when executed by the one or more processors, further cause the wireless device to:
receive a radio resource control message indicating that the cell comprises a downlink carrier, a normal uplink carrier, and a supplementary uplink carrier; and
select, based on a received signal strength of one of the plurality of downlink reference signals, at least one of the normal uplink carrier or the supplementary uplink carrier.
29 . The system of claim 25 , wherein the instructions, when executed by the one or more processors, further cause the wireless device to:
determine, based on the failure of the first LBT procedure, the resource for random access.
30 . The system of claim 25 , wherein the resource comprises a physical random access channel resource.
31 . The system of claim 25 , wherein the instructions, when executed by the one or more processors, further cause the wireless device to:
determine a second resource for random access, wherein the second resource is associated with a second downlink reference signal of the plurality of downlink reference signals of the cell; and
determine, based on the failure of the first LBT procedure, that the second resource is occupied.
32 . The system of claim 25 , wherein the instructions, when executed by the one or more processors, further cause the wireless device to:
perform, based on the failure of the first LBT procedure, a resource selection procedure for random access, wherein the resource selection procedure selects the resource.