Communications method and apparatus

1. A communication method, comprising:

receiving, by a core network element, a first request message from a terminal, wherein the first request message is used to request information used for PC5 interface-based communication of the terminal;

sending, by the core network element, a second request message to a policy and charging function (PCF) network element based on the first request message, wherein the second request message is used to request the information used for the PC5 interface-based communication;

receiving, by the core network element from the PCF network element, a quality of service (QoS) rule used for the PC5 interface-based communication; and

sending, by the core network element to the terminal and based on the first request message, the quality of service (QoS) rule, wherein the core network element is a mobility management network element.

2. The method according to claim 1 , wherein the method further comprises:

sending, by the core network element to a base station and based on the first request message, a QoS profile used for the PC5 interface-based communication.

3. The method according to claim 2 , wherein the method further comprises:

sending, by the core network element, first indication information to the base station, wherein the first indication information is used to indicate that the QoS profile is used for the PC5 interface-based communication.

4. The method according to claim 1 , wherein the first request message comprises second indication information, and wherein the second indication information is used to indicate that the first request message is used to request the information used for the PC5 interface-based communication.

5. The method according to claim 1 , wherein the first request message is a protocol data unit (PDU) session establishment message or a PDU session modification message, and wherein the method further comprises:

skipping triggering, by the core network element, establishment of an N3 tunnel and an N4 tunnel for a PDU session.

6. The method according to claim 2 , wherein the method further comprises:

receiving, by the core network element from the PCF network element, the QoS profile.

7. A communication method, comprising:

sending, by a core network element, a first request message to a policy and charging function (PCF) network element, wherein the first request message is used to request information used for PC5 interface-based communication of a terminal, wherein the core network element is a mobility management network element; and

sending, by the PCF network element to the core network element and based on the first request message, a policy and charging control (PCC) rule used for the PC5 interface-based communication; or

sending, by the PCF network element to the core network element and based on the first request message, at least one of a quality of service (QoS) rule or a QoS profile that is used for the PC5 interface-based communication.

8. The method according to claim 7 , wherein the first request message comprises indication information, and wherein the indication information is used to indicate that the first request message is used to request the information used for the PC5 interface-based communication.

9. The method according to claim 7 , further comprising:

receiving, by a base station, a second request message from the terminal, wherein the second request message is used to request information used for PC5 interface-based communication of the terminal;

sending, by the base station, the second request message to the core network element; and

receiving, by the base station and from the core network element, the QoS rule, and sending the QoS rule to the terminal.

10. The method according to claim 9 , wherein the method further comprises:

receiving, by the base station and from the core network element, the QoS profile.

11. The method according to claim 10 , wherein the method further comprises:

receiving, by the base station, indication information from the core network element, wherein the indication information is used to indicate that the QoS profile is used for the PC5 interface-based communication.

12. The method according to claim 9 , wherein the second request message is a protocol data unit (PDU) session establishment message or a PDU session modification message, and wherein the method further comprises:

skipping triggering, by the base station, establishment of at least one of an air-interface data radio bearer (DRB) or an N3 tunnel for a PDU session.

13. The method according to claim 9 , wherein the method further comprises:

receiving, by the base station, a scheduling request from the terminal, wherein the scheduling request comprises an identifier of the QoS rule; and

sending, by the base station, scheduled-resource information to the terminal based on the identifier of the QoS rule.

14. The method according to claim 7 , wherein the method further comprises:

receiving, by the core network element from the PCF network element, the QoS profile.

15. A communication system, comprising:

a core network element, configured to send a first request message to a policy and charging function (PCF) network element, wherein the first request message is used to request information used for PC5 interface-based communication of a terminal, wherein the core network element is a mobility management network element; and

the PCF network element, configured to:

send, to the core network element and based on the first request message, a policy and charging control (PCC) rule used for the PC5 interface-based communication; or

send, to the core network element and based on the first request message, at least one of a quality of service (QoS) rule or a QoS profile that is used for the PC5 interface-based communication.

16. The system according to claim 15 , wherein the first request message comprises indication information, and wherein the indication information is used to indicate that the first request message is used to request the information used for the PC5 interface-based communication.

17. The system according to claim 15 , wherein the core network element is configured to:

receive, from the PCF network element, the QoS profile.

18. The system according to claim 15 , wherein the core network element is further configured to:

receive a second request message from the terminal, wherein the second request message is used to request the information used for PC5 interface-based communication of the terminal.

19. The system according to claim 18 , wherein the core network element is further configured to:

send the QoS rule to the terminal based on the second request message.

20. The system according to claim 15 , wherein the core network element is further configured to:

send the QoS profile to a base station.