Direct communication

1 . A method, comprising:

transmitting, by a first user equipment (UE), to a second UE, a direct link establishment request message; and

receiving, by the first UE, from the second UE, a direct link establishment accept message, based on the direct link establishment request message,

wherein the direct link establishment request message includes one or more vehicle-to-everything (V2X) service identifiers and one or more security policies,

wherein, in a case where V2X services are mapped to security policies, when the first UE intends to establish a single unicast link that can be used for the V2X services, each of the security policies of the V2X services is compatible with one another, and

wherein a security policy of signalling integrity protection not needed and a security policy of signalling integrity protection required are not compatible.

2 . The method of claim 1 , further comprising:

transmitting, by the first UE, to a lower layer of the first UE, based on that the direct link establishment accept message has been received, information related to application of at least one of the security policies of the at least one of the V2X services.

3 . The method of claim 1 ,

wherein the direct link establishment accept message is a direct communication accept message.

4 . The method of claim 1 ,

wherein, based on that at least one of the security policies of the V2X services is compatible, the direct link establishment accept message includes a list of at least one of the V2X services accepted by the second UE.

5 . The method of claim 1 ,

wherein the direct link establishment accept message includes one or more security policies of the second UE for each of the V2X services.

6 . The method of claim 1 ,

wherein the security policy is a unicast signaling security policy of the first UE.

7 . The method of claim 1 , further comprising:

establishing, by the first UE, based on that each of the security policies of the V2X services is compatible, one or more quality of service (QoS) flows with the second UE.

8 . The method of claim 7 , further comprising:

mapping, by the first UE, the one or more QoS flows to one or more sidelink radio bearers (SLRBs),

wherein, for at least one QoS flow mapped to the one or more SLRBs, same security policy is applied.

9 . The method of claim 1 ,

wherein the case where the V2X services are mapped to the security policies is a case where different V2X services are mapped to different security policies.

10 . A first user equipment (UE), comprising:

at least one transceiver;

at least one processor; and

at least one memory connected to the at least one processor and storing instructions that, based on being executed by the at least one processor, cause the first UE to perform operations comprising:

transmitting, to a second UE, a direct link establishment request message; and

receiving, from the second UE, a direct link establishment accept message, based on the direct link establishment request message,

wherein the direct link establishment request message includes one or more vehicle-to-everything (V2X) service identifiers and one or more security policies,

wherein, in a case where V2X services are mapped to security policies, when the first UE intends to establish a single unicast link that can be used for the V2X services, each of the security policies of the V2X services is compatible with one another, and

wherein a security policy of signalling integrity protection not needed and a security policy of signalling integrity protection required are not compatible.

11 . The first UE of claim 10 ,

wherein the at least one memory connected to the at least one processor and storing the instructions that, based on being executed by the at least one processor, cause the first UE to perform the operations further comprising:

transmitting, to a lower layer of the first UE, based on that the direct link establishment accept message has been received, information related to application of at least one of the security policies of the at least one of the V2X services.

12 . The first UE of claim 10 ,

wherein the direct link establishment accept message is a direct communication accept message.

13 . The first UE of claim 10 ,

wherein, based on that at least one of the security policies of the V2X services is compatible, the direct link establishment accept message includes a list of at least one of the V2X services accepted by the second UE.

14 . The first UE of claim 10 ,

wherein the direct link establishment accept message includes one or more security policies of the second UE for each of the V2X services.

15 . The first UE of claim 10 ,

wherein the direct link establishment request message includes the strongest security policy among the security policies of the V2X services.

16 . The first UE of claim 10 ,

wherein the first UE is an autonomous driving device communicating with at least one of a mobile terminal, a network, and an autonomous vehicle other than the first UE.

17 . A processing device, comprising:

at least one processor; and

at least one memory connected to the at least one processor and storing instructions that, based on being executed by the at least one processor, cause a first user equipment (UE) to perform operations comprising:

transmitting, to a second UE, a direct link establishment request message; and

receiving, from the second UE, a direct link establishment accept message, based on the direct link establishment request message,

wherein the direct link establishment request message includes one or more vehicle-to-everything (V2X) service identifiers and one or more security policies,

wherein, in a case where V2X services are mapped to security policies, when the first UE intends to establish a single unicast link that can be used for the V2X services, each of the security policies of the V2X services is compatible with one another, and

wherein a security policy of signalling integrity protection not needed and a security policy of signalling integrity protection required are not compatible.