When users/UEs enter or leave vehicles with on board relays, handover between macro and vehicle relays can happen, if an active connection is ongoing.
The scenario described in this use case refers to a user, Alice, engaged in a phone call while going to her office via tram.
Alice is at a tram station, waiting for her usual 8am tram to get to her office, located several miles away.
The tram happens to be equipped with an on board base station relay, offering 5G connectivity from the same HPLMN as Alice is subscribed to.
Before the tram arrives, Alice calls her secretary to discuss the busy meetings schedule of the day, using available radio coverage from her HPLMN macro network.
While walking to the office building, Alice thanks her secretary for the helpful de-brief and hangs up; she feels very well prepared for the busy working day ahead.
Current requirements (e.g. related to wireless self-backhaul, see TS 22.261, clause 6.12
) or existing functionalities (e.g. IAB), cover scenarios of autonomous configuration/adaptation of network topologies, but do not assume or fully address physical relay mobility.
The 5G system shall be able to support efficient handover when a UE active communication changes from the macro network to a mobile base station relay (e.g. mounted on a vehicle) and vice versa, ensuring end-to-end service continuity during mobility of the UE (e.g. entering or leaving the vehicle) and/or the relay.