8.2.8 Constrained device selecting MSGin5G Relay UE or MSGin5G Proxy UE

23.5543GPPApplication architecture for MSGin5G ServiceRelease 18Stage 2TS

The signalling flow for MSGin5G Client in the MSGin5G UE-2 (which is a constrained device) to request other MSGin5G UEs having relay or proxy service capabilities to provide their configuration is illustrated in figure 8.2.8-1.

Pre-condition:

1) MSGin5G UE-2 is not able to communicate with MSGin5G Server directly;

2) MSGin5G UE-2 discovers nearby MSGin5G UEs using ProSe direct discovery procedure as specified in 3GPP TS 23.303 [19].

3) A MSGin5G UE-1 has both relay capability and proxy capability.

Figure 8.2.8-1: Constrained UE sending message to request configuration of the relay or proxy UE

1) The MSGin5G Client-2 in MSGin5G UE-2 (which is a constrained UE) sends message to all surrounding MSGin5G UE (using ProSe Direction communication as specified in 3GPP TS 23.303 [19]) to provide their relay or proxy configuration if relay or proxy service is supported by the MSGin5G UE. The request message includes information elements as specified in Table 8.2.8-1.

Table 8.2.8-1: Information elements for Request for relay or proxy UE configuration

Information element	Status	Description
Layer-2 ID	M	Layer-2 identity of UE-2
UE service ID	M	UE service identifier of the UE-2
MSGin5G UE ID	O	MSGin5G device identifier of the UE-2
Required packet size	M	Maximum allowed packet size of the UE-2

2) Upon receiving the request from the MSGin5G Client of MSGin5G UE-2, if MSGin5G UE-1 supports the relay or proxy service capability, the MSGin5G Client-1 sends the response for the relay or proxy configuration. The response message includes information elements as specified in Table 8.2.8-2.

Table 8.2.8-2: Information elements for Response for relay or proxy UE configuration

Information element	Status	Description
Layer-2 ID	M	Layer-2 identity of UE-1
UE service ID	M	UE service identifier of the UE-1
MSGin5G UE ID	O	MSGin5G device identifier of the UE-1
Allowed packet size	M	Maximum allowed packet size of the UE-2

3) If the MSGin5G UE-2 receives responses from multiple different relay or proxy UEs (i.e. MSGin5G UE-1 with support for the relay or proxy service), then the MSGin5G Client of the MSGin5G UE-2 selects MSGin5G UE-1 (with the relay or proxy service) whose value of the Allowed packet size is equal or more than the value of the Required packet size of the MSGin5G UE-2. If value of the Allowed packet size is less than the value of the Required packet size for all MSGin5G UE-1s (i.e. relay or proxy UEs), then the MSGin5G Client of the MSGin5G UE-2 selects the MSGin5G UE-1 (with relay or proxy service) with the maximum value of the Allowed packet size among all MSGin5G UE-1s and further sets the maximum allowed packet size of the constrained UE to the value of the Allowed packet size of the selected MSGin5G UE-1 (i.e. relay or proxy UE).

Once MSGin5G UE-2 selects the MSGin5G Relay UE or MSGin5G Proxy UE, the MSGin5G UE-2 indicates the selected MSGin5G UE by registering to use the relay or proxy service. The signalling flow for MSGin5G Client in the MSGin5G UE-2 (which is a constrained device) to register itself to use relay or proxy service of the MSGin5G Relay UE or MSGin5G Proxy UE is illustrated in figure 8.2.8-2.

Figure 8.2.8-2: Constrained UE registering to use relay UE

1) Upon selecting the relay or proxy UE, the MSGin5G Client-2 of the MSGin5G UE-2 sends request message to register with the selected MSGin5G Relay UE or MSGin5G Proxy UE to indicate it about the use of relay service or proxy service by the MSGin5G UE-2 (i.e. constrained device). The request message may also include the other required parameters like UE service ID and MSGin5G UE ID of the MSGin5G UE-2 (i.e. constrained UE) and the time till when constrained device is intended to use the relay or proxy service from the selected Relay or Proxy UE.

2) Upon receiving the request from the MSGin5G Client-2 of the MSGin5G UE-2, the MSGin5G Client-1 checks whether the MSGin5G UE-2 is authorized to use the relay service or not. And if the MSGin5G UE-2 is authorized, the MSGin5G Client-1 sends the response message with the status of the registration. If the registration is success, the response message also includes other parameters like the accepted time till when constrained device is allowed to use the relay or proxy service from the selected MSGin5G Relay UE or MSGin5G Proxy UE.