Radio Link Control (RLC) Retransmission with L1/L2 Triggered Mobility (LTM) Cell Switch

A method for a user equipment (UE) configured to communicate with a radio access network (RAN) node, the method comprising:

• receiving, from the RAN node via a serving cell, a lower layer signalling message indicating that the UE should perform an layer-1/layer-2 triggered mobility (LTM) procedure from the serving cell to a first candidate cell;
• executing the LTM procedure towards the first candidate cell, including performing a reset of a first protocol layer used for communicating with the serving cell;
• and
• after executing the LTM procedure, initiating retransmission in the first candidate cell of protocol data units (PDUs) of a second protocol layer, which were lost or discarded due to the reset of the first protocol layer.

User equipment (UE) configured to communicate with a radio access network (RAN) node, the UE comprising:

• communication interface circuitry configured to communicate with the RAN node via at least one serving cell;
• and
• processing circuitry operably coupled to the communication interface circuitry, wherein the processing circuitry and communication interface circuitry are configured to:
• receive, from the RAN node via the serving cell, a lower layer signalling message indicating that the UE should perform an layer-1/layer-2 triggered mobility (LTM) procedure from the serving cell to a first candidate cell;
• execute the LTM procedure towards the first candidate cell, including performing a reset of a first protocol layer used for communicating with the serving cell;
• and
• after executing the LTM procedure, initiate retransmission in the first candidate cell of protocol data units (PDUs) of a second protocol layer, which were lost or discarded due to the reset of the first protocol layer.

Radio access network (RAN) node configured to provide a serving cell to user equipment (UEs), the RAN node comprising:

• communication interface circuitry configured to communicate with UEs via the serving cell;
• and
• processing circuitry operably coupled to the communication interface circuitry, wherein the processing circuitry and the communication interface circuitry are configured to:
• send, to the UE via the serving cell, a lower layer signalling message indicating that the UE should perform an layer-1/layer-2 triggered mobility (LTM) procedure from the serving cell to a first candidate cell, including UE reset of a first protocol layer used for communicating with the serving cell;
• and
• initiate retransmission in the first candidate cell of protocol data units (PDUs) of a second protocol layer, which were lost or discarded due to the UE reset of the first protocol layer.