ProSe Proxy Function enables support for UE to Home ProSe Function/ProSe Key Management Function communication as defined in clause 188.8.131.52
and in TS 33.303
, where the Home ProSe Function/ProSe Key Management Function is not located in the same network as the PDN GW for the PDN connection being used. Such proxy functions are needed when requirements on security are not met by signalling over Internet. Inter-PLMN signalling may be used in that case. Due to restrictions on the inter-PLMN network, the UE to Server traffic over the user plane may not be sent between networks directly. Only tunnelled server to server traffic may be sent between networks.
A roaming UE, which has a Local Breakout PDN Connection in the VPLMN, uses this access to reach a ProSe Function in the Home network and a ProSe Key Management Function in the Home network or another network. UE is not aware of the presence of a ProSe Proxy Function.
A ProSe Proxy implemented in the VPLMN on the SGi interface may be used to reach the ProSe Function located in the HPLMN. The ProSe Proxy Function forwards signalling traffic between the UE and the ProSe Function in the HPLMN.
A ProSe Proxy implemented in either the HPLMN or the VPLMN on the SGi interface may be used to reach a ProSe Key Management Function located in a different network. The ProSe Proxy Function forwards the signalling traffic (as defined in clause 184.108.40.206.1 in TS 33.303
) between the UE and the ProSe Key Management Function.
ProSe-enabled non-Public Safety UE shall not use ProSe when in limited service state.
ProSe-enabled Public Safety UEs that are authorised to use ProSe Direct Communication and/or ProSe Direct Discovery shall be able to use ProSe Direct Communication and/or ProSe Direct Discovery when in limited service state following the procedures defined in clause 220.127.116.11.2.3.1
for ProSe Direct Communication and ProSe Direct Discovery when the UE enters in limited service state:
because it cannot find a suitable cell of the selected PLMN as described in TS 23.122 or
as the result of receiving one of the following reject reasons defined in TS 23.122:
a "PLMN not allowed" response to a registration request or;
a "GPRS not allowed" response to a registration request
A ProSe-enabled Public Safety UE in limited service state shall only use ProSe mechanisms available in ECM-IDLE, for details see TS 36.300
A ProSe-enabled Public Safety UE in limited service state shall not use ProSe in ECM-CONNECTED mode.
ProSe-enabled Public Safety UEs shall not use ProSe Direct Communication or ProSe Direct Discovery if the UE has entered in limited service state due to all other situations (e.g. no SIM in the MS, an "illegal MS" or "illegal ME" response to a registration request, or an "IMSI unknown in HLR" response to a registration request) defined in TS 23.122
, where the UE is unable to obtain normal service from a PLMN.