Channel access priority class for signaling radio bearers in new radio unlicensed
A method for determining Listen Before Talk (LBT) type and Channel Access Priority Class (CAPC) for signaling message transmission over signaling radio bearers (SRBs) in 5G New Radio-Unlicensed (NR-U) is proposed. A user equipment (UE) generates an SRB message to be transmitted to a serving base station over a control channel. Before the uplink (UL) transmission of an UL PDU containing the SRB message, the UE performs an LBT procedure using a set of LBT parameters associated with a CAPC value. In one embodiment, the CAPC is provided by the base station via an UL grant contained in a downlink control information (DCI). In another embodiment, the CAPC is determined by the UE based on an SRB type of the SRB message.
1. A method comprising:
establishing a connection by a user equipment (UE) with a base station over an unlicensed band, wherein the connection comprises one or more signaling radio bearers (SRBs);
generating an SRB message; wherein the SRB message is transmitted to the base station over a control channel;
performing a listen-before-talk (LBT) procedure using a set of LBT parameters associated with a channel access priority class (CAPC), wherein the UE obtains the CAPC corresponds to the SRB message; wherein the set of LBT parameters comprises LBT type, length of cyclic prefix (CP) extension, and CAPC value; and
transmitting the SRB message over the control channel upon successfully completing the LBT procedure;
wherein the UE multiplexes the SRB message and subsequent messages to be transmitted in one uplink protocol data unit (PDU).
2. The method of claim 1 , wherein the CAPC is obtained from an uplink grant for the SRB message provided by the base station.
3. The method of claim 1 , wherein the CAPC is assigned by the UE based on an SRB type of the SRB message.
4. The method of claim 1 , wherein the SRB message belongs to one of SRB types including SRB0, SRB1, SRB2, and SRB3 type.
5. The method of claim 4 , wherein a higher CAPC priority value is assigned to SRB messages having SRB0, SRB1, or SRB3 type.
6. The method of claim 4 , wherein a lower CAPC priority value is assigned to SRB messages having SRB2 type.
7. The method of claim 1 , wherein the UE selects a highest priority across all multiplexed messages to perform the LBT procedure.
8. The method of claim 1 , wherein the UE selects a lowest priority across all multiplexed messages to perform the LBT procedure.
9. The method of claim 1 , wherein the UE performs another LBT procedure for a subsequent uplink transmission after reaching a maximum channel occupancy time (MCOT).
10. A User Equipment (UE), comprising:
a radio bearer handling circuit that establishes a connection with a base station over an unlicensed band, wherein the connection comprises one or more signaling radio bearers (SRBs);
an uplink channel handling circuit that generates an SRB message; wherein the SRB message is transmitted to the base station over a control channel;
a listen-before-talk (LBT) handling circuit that performs an LBT procedure using a set of LBT parameters associated with a channel access priority class (CAPC), wherein the UE obtains the CAPC corresponds to the SRB message; wherein the set of LBT parameters comprises LBT type, length of cyclic prefix (CP) extension, and CAPC value; and
a transmitter that transmits the SRB message over the control channel upon successfully completing the LBT procedure;
wherein the UE multiplexes the SRB message and subsequent messages to be transmitted in one uplink protocol data unit (PDU).
11. The UE of claim 10 , wherein the CAPC is obtained from an uplink grant for the SRB message provided by the base station.
12. The UE of claim 10 , wherein the CAPC is assigned by the UE based on an SRB type of the SRB message.
13. The UE of claim 10 , wherein the SRB message belongs to one of SRB types including SRB0, SRB1, SRB2, and SRB3 type.
14. The UE of claim 13 , wherein a higher CAPC priority value is assigned to SRB messages having SRB0, SRB1, or SRB3 type.