Network slice information for handover procedure

A first base station comprising:

• one or more processors;
• and
• memory storing instructions that, when executed by the one or more processors, cause the first base station to:
• receive, from a core network entity, a first message indicating a request for session resources for a wireless device, wherein the session resources are for a first network slice;
• initiate, based on the requested session resources for the first network slice not being available for the wireless device at the first base station, a handover for the wireless device towards a first cell of a second base station;
• send, to the second base station and based on the initiating, a second message indicating a handover request, the second message comprising:
• a packet flow identifier of a packet flow associated with the first network slice;
• a network slice identifier of the first network slice for the handover request;
• and
• a cause information element indicating that a cause for the handover request is that the requested session resources are not available, at the first base station, for the first network slice identified by the network slice identifier;
• and
• receive, from the second base station, a third message indicating an acceptance or a rejection based on the second message.

A method comprising:

• receiving, by a first base station from a second base station, a first message indicating a handover request based on requested session resources for a first network slice not being available for a wireless device at the first base station, the first message comprising:
• a packet flow identifier of a packet flow associated with a first network slice of a plurality of network slices;
• a network slice identifier of the first network slice for the handover request;
• and
• a cause information element indicating that a cause for the handover request is that the requested session resources are not available, at the first base station, for the first network slice identified by the network slice identifier;
• and
• sending, to the second base station, a second message indicating an acceptance or a rejection based on the first message.