An MC gateway UE enables MC service access for a MC service user residing on non-3GPP capable devices and for devices which are unable to host MC service clients. In order to be able to participate in a MC service, the MC gateway UE provides the following necessary functions to enable the MC service access for such MC clients:
MC gateway client to MC gateway UE association: Authorised binding and use of non-3GPP based access with an MC service client. It indicate the associated MC gateway clients when the MC gateway UE cannot serve the connected MC service clients (any longer).
3GPP transport resources: Sharing of MC gateway UE 3GPP transport resources among the associated MC service clients.
MC client identification: Independent MC service client identification, MC service client authorisation and MC service profile association.
Location Management: Providing location management support for the associated MC clients to handle the location information and triggers related to 3GPP access network.
MC client communication integrity: Ensure that signalling, media content and traffic attributes, e.g. priority and QoS, of communications between the MC system and MC service client remains unaltered.
The following functions are provided by the MC gateway client:
MC gateway UE association: Allowing an MC gateway client to simultaneously bind to multiple MC gateway UEs.
MC service selection: Choose between multiple MC gateway UEs for the required MC service capability.
MC service continuation: Enables reselection of the MC gateway UE association while MC service continues.
The MC gateway UE offers access to the MC server for several MC clients as shown in Figure 11.2.0-1. The MC clients can be either located in the MC gateway UE or in non-3GPP devices connected to the MC gateway UE via non-3GPP access.
For non-3GPP devices which can host an MC client, the MC gateway UE enables connectivity to the MC server. For non-3GPP devices which cannot host the MC client, the MC gateway UE hosts the instantiation of the MC client for the non-3GPP device.
The MC gateway UE provides MC service capabilities and 3GPP access capabilities using 3GPP network credentials for authorized access with an MC server.
For non-3GPP devices which cannot host MC clients, the MC gateway UE shall control the access and manage the communication between the non-3GPP devices and the MC server. Upon reception of connection authorization request from a non-3GPP device, the MC gateway UE instantiates an MC client, acting on behalf of the non-3GPP device, to provide the requested services (e.g. emergency call, group calls, short data messages services, etc.). The communication interworking and the definition of associated procedures between the MC client (initiated at the MC gateway UE) and the non-3GPP devices is out of scope of this document.
For MC clients getting MC service access via the MC gateway UE, the MC gateway UE forwards (unmodified) signalling and media from the individual MC clients to the MC server and vice versa.
If the MC service user on the non-3GPP device utilizes multiple MC services simultaneously, the MC service access may also be provided by one or multiple MC gateway UEs as shown in Figure 11.2.0-2 while restricting each MC service to one MC gateway UE (e.g. MCPTT via MC gateway UE1, MCData via MC gateway UE2).
For the application-level signalling necessary for the association between the MC client on the non-3GPP device and the MC gateway UE reference point Gateway-local (GW-local) is used. The MC gateway UE uses the Gateway-Core (GW-Core) reference point towards the MC service server to announce the association between MC gateway client and MC gateway UE server. Once the use of the MC gateway UE has been authenticated and authorized by the corresponding MC service server, the MC service user is authorized MC gateway user.
The MC gateway UE sever enables the following functions:
Authentication of the MC gateway clients including the MC gateway UE function of the corresponding MC service server
The following functions are available when the connection authorization of the MC gateway client is successful:
Relay of signalling between MC client and MC service server/CSC server
Relay of signaling between the signaling user agent residing on the non-3GPP device and the SIP core
Relay of signaling between the HTTP client residing on the non-3GPP device and the HTTP proxy
Media plane forwarding between the MC service server and the MC clients
The MC gateway UE function as part of the corresponding MC service server enables the use of an MC gateway UE with a corresponding MC gateway UE function that authorizes the association between the MC gateway client/MC client and the corresponding MC gateway UE to enable forwarding of the media plane to MC clients via the MC gateway UE.
The GW-local reference point between the MC gateway client and the MC gateway UE server in the MC gateway UE is used:
To authorize the use of the MC gateway UE,
To manage (request/release) forwarding of the signalling, media from the MC gateway UE to the MC gateway client and its associated MC clients for unicast, multicast/broadcast communication using corresponding identifiers, e.g., TMGI,
To disconnect from the use of the MC gateway UE.
To notify about the connection status.
The GW-local reference point is based on HTTP.
The reference points CSC-n belonging to the application plane and the reference points SIP-1 and HTTP-1 belonging to the signaling control plane are relayed by the MC gateway UE between MC client on the non-3GPP device towards the MC gateway UE and the corresponding MC service server.
CSC-n, SIP-1 and HTTP-1 reference points are specified in the present specification. The MCX-n reference points are specified in TS 23.379, TS 23.281 and TS 23.282.
The MC gateway UE forms the relay unit for the media plane between MC server and MC client using 3GPP transport resources on one hand and non-3GPP transport resources on the other hand. The media forwarding function relays the media traffic for unicast and multicast/broadcast between the 3GPP connectivity and non-3GPP connectivity following the media forwarding request controlled by the MC gateway UE server. For the use of unicast media and multicast/broadcast media the corresponding reference points of the respective MC service applies. The corresponding media parameter applies between the respective service dependent media function and service dependent media distribution function.