Reporting inter-RAT mobility failures

A method for a network node to handle failed inter-RAT mobility procedures of user equipment, UEs, in a wireless network, the method comprising:

• receiving a failure report about a UE's failed inter-RAT mobility procedure from a source cell served by a source node to a target cell served by a target node, wherein the target cell uses a different RAT than the source cell, and wherein the failure report indicates one of the following failure causes:
• that the UE was unable to comply with a configuration included in a command to perform the inter-RAT mobility procedure, or
• a protocol error associated with inter-RAT information included in the command,
• wherein the indication of the failure cause is one of the following:
• an explicit indication of the failure cause, or an implicit indication of the failure cause based on the failure report indicating handover failure but omitting information about random access;
• and
• based on the failure cause indication, performing one or more operations that prevent failures in subsequent mobility procedures involving the source cell and/or the target cell.

A user equipment (UE) configured to report failure of an inter-radio access technology (RAT) mobility procedure from a source cell to a target cell in a wireless network, the UE comprising:

• radio transceiver circuitry configured to communicate with one or more network nodes in the wireless network;
• and
• processing circuitry operatively coupled to the radio transceiver circuitry, whereby the processing circuitry and the radio transceiver circuitry are configured to:
• receive, from a source node serving the source cell, a command to perform an inter-RAT mobility procedure towards the target cell, wherein the target cell uses a different RAT than the source cell;
• detect a failure associated with the inter-RAT mobility procedure, wherein the failure cause is one of the following:
• that the UE was unable to comply with a configuration included in the command, or
• a protocol error associated with inter-RAT information included in the command;
• and
• send a failure report, including an indication of the failure cause, to a node serving a cell in which the UE connected to the wireless network after detecting the failure, wherein the indication of the failure cause is one of the following:
• an explicit indication of the failure cause, or
• an implicit indication of the failure cause based on the failure report indicating handover failure but omitting information about random access.