Methods and apparatuses for reflective quality of service (QoS)

1 . A method performed by a relay user equipment (UE) that has a PC5 link with a remote UE, the method comprising:

receiving a downlink (DL) packet;

adding one or more reflective quality-of-service (QoS) indicators to the DL packet, thereby creating a modified DL packet containing one or more reflective QoS indicators; and

transmitting the modified DL packet containing the one or more reflective QoS indicators on the PC5 link in a PC5 QoS flow to the remote UE, wherein

the method further comprises:

receiving a UE capability indicator transmitted by the remote UE, wherein the UE capability indicator indicates whether the remote UE supports reflective QoS on a PC5 link;

using the received UE capability indicator to determine that the remote UE supports reflective QoS on a PC5 link;

transmitting the UE capability indicator that indicates whether the remote UE supports reflective QoS on a PC5 link to a network node or a second relay UE;

transmitting a UE capability indicator that indicates whether the relay UE supports reflective QoS on a PC5 link to a network node or a second relay UE; and

receiving service information transmitted by the remote UE, wherein the service information indicates whether the remote UE will adopt or allow reflective QoS for each of one or more services, and

the relay UE adds the one or more reflective QoS indicators to the DL packet in response to determining that the remote UE supports reflective QoS on a PC5 link.

2 . The method of claim 1 , further comprising determining whether the received DL packet is for the relay UE or for the remote UE; and

wherein the received DL packet includes a target Internet Protocol (IP) address, and the target IP address is used to determine whether the received DL packet is for the relay UE or for the remote UE; and/or

wherein the received DL packet includes a QoS Flow Identifier (QFI), and the QFI is used to determine whether the received DL packet is for the relay UE or for the remote UE.

3 . The method of claim 1 , wherein the one or more reflective QoS indicators include a QoS Flow Identifier (QFI), a data radio bearer (DRB) mapping indication (RDI), and/or a reflective QoS indication (RQI).

4 . The method of claim 1 , wherein the relay UE has a Uu link with a network node, and the received DL packet is transmitted by the network node on the Uu link in a Uu QoS flow; and

wherein the method further comprises deriving one or more mapping relations from the received DL packet;

wherein the received DL packet includes a header, and the one or more mapping relations are derived using the header; and/or

wherein the DL packet is a service data adaptation protocol (SDAP) packet data unit (PDU), and the one or more mapping relations are derived using an SDAP header of the SDAP PDU.

5 . The method of claim 4 , further comprising:

receiving an uplink (UL) packet transmitted by the remote UE on the PC5 link in the PC5 QoS flow; and

applying the one or more derived mapping relations to map the UL packet to the Uu QoS flow and transmit the UL packet on the Uu link to the network node.

6 . The method of claim 4 , further comprising using the derived one or more mapping relations to determine a PC5 QoS Flow Identifier (PFI) for the received DL packet;

wherein the received DL packet includes a QoS Flow Identifier (QFI), and the PFI is determined using the QFI of the received DL packet and a table that maps QFIs to PFIs.

7 . The method of claim 4 , further comprising determining a PC5 data radio bearer (DRB), wherein the determined PC5 DRB is used to carry the PC5 QoS flow; and

receiving an uplink (UL) packet transmitted by the remote UE on the PC5 link in the PC5 QoS flow carried by the PC5 DRB;

wherein a Uu DRB carries the Uu QoS flow, and determining the PC5 DRB comprises comparing the PC5 DRB and the Uu DRB;

wherein comparing the PC5 DRB and the Uu DRB considers the QoS configurations of the PC5 DRB and the Uu DRB, of any existing flows being mapped to the PC5 DRB, and/or of any existing flows being mapped to the Uu DRB, the QoS configurations include one or more QoS parameters, and the one or more QoS parameters include priority index, bit rate, packet error rate, latency, packet loss, and/or jitter; and

wherein comparing the PC5 DRB and the Uu DRB considers free capacity or resources on the PC5 DRB and/or free capacity or resources on the Uu DRB.

8 . The method of claim 7 , wherein the determined PC5 DRB is a PC5 DRB that is mapped or associated with the Uu DRB that carries the Uu QoS flow; or

wherein the determined PC5 DRB is a PC5 DRB that is associated with similar QoS parameters as the Uu DRB that carries the Uu QoS flow; or

wherein the determined PC5 DRB is a PC5 DRB that is able to achieve similar QoS satisfaction as the Uu DRB that carries the Uu QoS flow, and whether the PC5 DRB is able to achieve similar QoS satisfaction as the Uu DRB that carries the Uu QoS flow is determined based on how much free sources each of the PC5 DRB and the Uu DRB are able to provide and/or the priority orders of the PC5 DRB and the Uu DRB.

9 . The method of claim 7 , further comprising starting or re-starting a timer when one or more reflective mapping relations for the PC5 DRB are established, changed, or reconfigured, wherein the reflective mapping relations are valid for the PC5 DRB while the timer is running and invalid when the timer is expired.

10 . The method of claim 1 , wherein the received DL packet includes a header, the one or more reflective QoS indicators are added to the header of the DL packet, the DL packet is a service data adaptation protocol (SDAP) packet data unit (PDU), and the one or more reflective QoS indicators are added to an SDAP header of the SDAP PDU.

11 . The method of claim 1 , further comprising receiving an uplink (UL) packet transmitted by the remote UE on the PC5 link in the PC5 QoS flow.

12 . The method of claim 11 , wherein the relay UE has a Uu link with a network node, the received DL packet was transmitted by the network node on the Uu link in a Uu QoS flow, and the method further comprises transmitting the UL packet on the Uu link in the Uu QoS flow to the network node.

13 . The method of claim 1 , wherein the relay UE has a second PC5 link with a second relay UE, and the received DL packet was transmitted by the second relay UE on the second PC5 link in a second PCF QoS flow;

the method further comprises:

receiving an uplink (UL) packet transmitted by the remote UE on the PC5 link in the PC5 QoS flow;

transmitting the UL packet on the second PC5 link in the second PC5 QoS flow to the second relay UE; and

the method further comprises one or more of:

deriving one or more mapping relations from the received DL packet;

applying the one or more derived mapping relations to map the UL packet to the second PC5 QoS flow and transmit the UL packet on the second PC5 link to the second relay UE;

using the derived one or more mapping relations to determine a PC5 QoS Flow Identifier (PFI) for the received DL packet; and

determining a PC5 data radio bearer (DRB), wherein the determined PC5 DRB is used to carry the PC5 QoS flow.

14 . The method of claim 1 , further comprising:

for a UE to network relay, maintaining a mapping table between PC5 QoS Flow Identifiers (PFIs) and QoS Flow Identifiers (QFIs); or

for UE to UE relay, using the same QoS Flow Identifiers (QFIs) for all interconnected flows between two hops.

15 . A relay user equipment (UE) comprising:

processing circuitry; and

a memory, said memory containing instructions executable by said processing circuitry, whereby the relay UE is operative to:

receive a downlink (DL) packet;

add one or more reflective quality-of-service (QoS) indicators to the DL packet, thereby creating a modified DL packet containing one or more reflective QoS indicators; and

transmit the modified DL packet containing the one or more reflective QoS indicators on a PC5 link in a PC5 QoS flow to a remote UE, wherein

the UE is further operative to:

receive a UE capability indicator transmitted by the remote UE, wherein the UE capability indicator indicates whether the remote UE supports reflective QoS on a PC5 link;

use the received UE capability indicator to determine that the remote UE supports reflective QoS on a PC5 link;

add the one or more reflective QoS indicators to the DL packet in response to determining that the remote UE supports reflective QoS on a PC5 link;

transmit the UE capability indicator that indicates whether the remote UE supports reflective QoS on a PC5 link to a network node or a second relay UE;

transmit a UE capability indicator that indicates whether the relay UE supports reflective QoS on a PC5 link to a network node or a second relay UE; and

receive service information transmitted by the remote UE, wherein the service information indicates whether the remote UE will adopt or allow reflective QoS for each of one or more services.

16 . The method of claim 1 , wherein,

the method further comprises receiving a UE capability indicator transmitted by the remote UE, and

the one or more reflective QoS indicators are added to the DL packet in response to determining, based on the UE capability indicator, that the remote UE supports reflective QoS on a PC5 link.