10.5 Use of UE-to-network relay

23.2803GPPCommon functional architecture to support mission critical servicesRelease 18Stage 2TS

10.5.1 UE-to-network relay service authorization

The MC service shall support the capability for UE-to-network relay to restrict the relayed group communication on a per group basis.

To meet the above requirement, ProSe (as specified in 3GPP TS 23.303 [14]) can be used with an appropriate relay service code as per the following:

– To restrict connection from only the membership of allowed MC service groups, UE-to-network relay UE is provisioned with relay service code(s) associated with allowed MC service group(s). The UE-to-network relay performs the access control as follows:

1) The UE broadcasts which MC service group(s) is/are authorized to connect to the network over this UE-to-network relay by including the related relay service code(s) in the UE-to-Network Relay Discovery Announcement message (as specified in 3GPP TS 23.303 [14]); or

2) The UE determines whether to respond to a remote UE’s broadcasting message by checking if the relay service code carried in the UE-to-Network Relay Discovery Solicitation message is within the list of allowed relay service codes.

– To find a permitted UE-to-network relay, a remote UE is provisioned with the relay service code(s) associated MC service group(s) which the MC service user belongs to. The remote UE performs the UE-to-network relay selection as follows:

1) The remote UE determines if it is allowed to connect to a particular UE-to-network relay by checking whether the relay service code(s) associated with its MC service group(s) is/are carried in UE-to-Network Relay Discovery Announcement message (as specified in 3GPP TS 23.303 [14]; or

2) The remote UE includes the relay service code(s) associated with its MC service group(s) in Network Relay Discovery Solicitation message (as specified in 3GPP TS 23.303 [14]).

10.5.2 UE-to-network relay MC service

The ProSe UE-to-network relay provides a purely layer 3 IP data routing service, when the remote UE loses the coverage of cellular network and the MC service user on the remote UE requires to access the MC service via a ProSe UE-to-network relay.

The application layer signalling for the MC service user on a remote UE are identical to the application layer signalling for the MC service user on an on network UE.